<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:79d5254a-d034-4889-a5fe-84dd5f499622,g:6939ee2d-7383-4d9c-b79c-1739592c81a6-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://seer.bio/role/CoverPage" xlink:type="simple" xlink:href="seer-20230630.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CoverPage" xlink:type="extended" id="ie1253ae4abed4d53ab4d0327253ed178_CoverPage">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_d3251763-5f0a-4ea1-81f4-f160e70d45e1" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentType_d3251763-5f0a-4ea1-81f4-f160e70d45e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_01486641-99d8-44f4-be54-41a3f1056812" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentQuarterlyReport_01486641-99d8-44f4-be54-41a3f1056812" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_339a8a73-bdaf-4c3e-b94c-6e93a6e76435" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentPeriodEndDate_339a8a73-bdaf-4c3e-b94c-6e93a6e76435" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_0cc3ff55-90df-4b1a-bbd2-de21feb913c2" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentTransitionReport_0cc3ff55-90df-4b1a-bbd2-de21feb913c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_58e2da75-a0bf-452e-a911-a25d7e9aaf5a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityFileNumber_58e2da75-a0bf-452e-a911-a25d7e9aaf5a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_59a68d0b-580d-4eed-bcb7-a6ee3ba0d0e8" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityRegistrantName_59a68d0b-580d-4eed-bcb7-a6ee3ba0d0e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_b18fecb5-fcdf-46ee-8d49-a3955f8d85b0" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityIncorporationStateCountryCode_b18fecb5-fcdf-46ee-8d49-a3955f8d85b0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_2170c74a-0b56-45fd-81df-0d1be8ec82af" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityTaxIdentificationNumber_2170c74a-0b56-45fd-81df-0d1be8ec82af" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_39de0f30-c23f-40d0-8b81-a975803b8b2d" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityAddressAddressLine1_39de0f30-c23f-40d0-8b81-a975803b8b2d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_b47a880b-7a80-4e4d-8337-2d79b40e0eab" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityAddressAddressLine2_b47a880b-7a80-4e4d-8337-2d79b40e0eab" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_56ab6726-6fb4-4a5b-92e7-be318404bdde" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityAddressCityOrTown_56ab6726-6fb4-4a5b-92e7-be318404bdde" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_ead8858e-faa7-4651-8521-8fb644412c25" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityAddressStateOrProvince_ead8858e-faa7-4651-8521-8fb644412c25" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_62dd425e-a537-4d4a-8149-afabde686307" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityAddressPostalZipCode_62dd425e-a537-4d4a-8149-afabde686307" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_04900a38-fa21-48ad-9969-3e09f9d163ab" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_CityAreaCode_04900a38-fa21-48ad-9969-3e09f9d163ab" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_9f435dbd-1477-4fd9-9c88-07f553247cf8" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_LocalPhoneNumber_9f435dbd-1477-4fd9-9c88-07f553247cf8" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_68b00faa-b93a-4767-bd3a-51e752a2a47e" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_Security12bTitle_68b00faa-b93a-4767-bd3a-51e752a2a47e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_3efeac69-ba7d-483b-8538-eefc4e4e5c8a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_TradingSymbol_3efeac69-ba7d-483b-8538-eefc4e4e5c8a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_f1bf8daa-d8fa-4428-b1fc-46600578cb52" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_SecurityExchangeName_f1bf8daa-d8fa-4428-b1fc-46600578cb52" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_cfeb5d66-94fd-4f64-ba8c-ec08f77fd41f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityCurrentReportingStatus_cfeb5d66-94fd-4f64-ba8c-ec08f77fd41f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_fee2abf2-2ab6-455e-89b1-284fd61ca910" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityInteractiveDataCurrent_fee2abf2-2ab6-455e-89b1-284fd61ca910" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_f306becd-9eac-4472-9773-b499b071134b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityFilerCategory_f306becd-9eac-4472-9773-b499b071134b" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_4ccff0d9-8c57-46ba-9800-164e48905840" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntitySmallBusiness_4ccff0d9-8c57-46ba-9800-164e48905840" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_c51a267d-ff57-4926-8a47-d29d1e6db789" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityEmergingGrowthCompany_c51a267d-ff57-4926-8a47-d29d1e6db789" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_f271920d-fd9a-4ddb-8c50-bb86e825ab03" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityShellCompany_f271920d-fd9a-4ddb-8c50-bb86e825ab03" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_0cbf4d4c-e5dc-41ba-9d96-b35075cbe94b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_0cbf4d4c-e5dc-41ba-9d96-b35075cbe94b" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_b5d6dd2f-95be-427c-b0f4-d4c65de9af7f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_EntityCentralIndexKey_b5d6dd2f-95be-427c-b0f4-d4c65de9af7f" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_539cc681-9606-4a37-8308-3599ddc7d128" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_CurrentFiscalYearEndDate_539cc681-9606-4a37-8308-3599ddc7d128" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_fdee0f3f-a6dc-47bd-a188-634e11514abb" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentFiscalYearFocus_fdee0f3f-a6dc-47bd-a188-634e11514abb" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_d34c39e0-8a67-4846-a0ea-40df6f7e0189" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentFiscalPeriodFocus_d34c39e0-8a67-4846-a0ea-40df6f7e0189" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_55940cf4-d4fe-40a4-8f86-b9f04a3a8719" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_AmendmentFlag_55940cf4-d4fe-40a4-8f86-b9f04a3a8719" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_4a995e6f-c65e-4460-a6cc-bf5e204e6d4f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_516fea73-66db-4dd7-a316-7b3c55876fdd" xlink:to="loc_dei_DocumentInformationTable_4a995e6f-c65e-4460-a6cc-bf5e204e6d4f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_0610a933-96b7-458c-ac56-ca30d260dfac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_4a995e6f-c65e-4460-a6cc-bf5e204e6d4f" xlink:to="loc_us-gaap_StatementClassOfStockAxis_0610a933-96b7-458c-ac56-ca30d260dfac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_0610a933-96b7-458c-ac56-ca30d260dfac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_0610a933-96b7-458c-ac56-ca30d260dfac" xlink:to="loc_us-gaap_ClassOfStockDomain_0610a933-96b7-458c-ac56-ca30d260dfac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_46aedd1a-519b-4499-a370-b828ea3c33dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_0610a933-96b7-458c-ac56-ca30d260dfac" xlink:to="loc_us-gaap_ClassOfStockDomain_46aedd1a-519b-4499-a370-b828ea3c33dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_bbef738b-080f-4fe7-a255-672742724b84" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_46aedd1a-519b-4499-a370-b828ea3c33dd" xlink:to="loc_us-gaap_CommonClassAMember_bbef738b-080f-4fe7-a255-672742724b84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_a2dc1bba-4a8b-42b0-a373-1f2cdb1c9b47" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_46aedd1a-519b-4499-a370-b828ea3c33dd" xlink:to="loc_us-gaap_CommonClassBMember_a2dc1bba-4a8b-42b0-a373-1f2cdb1c9b47" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="simple" xlink:href="seer-20230630.xsd#CondensedConsolidatedBalanceSheetsUnaudited"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="extended" id="i31e3359097f24658a383e8fe04016534_CondensedConsolidatedBalanceSheetsUnaudited">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_85f81a84-da04-48e1-988f-f4afeaf97d27" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_85f81a84-da04-48e1-988f-f4afeaf97d27" xlink:to="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_fd8ee547-88ef-416d-b937-c98c1f7b83ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_fd8ee547-88ef-416d-b937-c98c1f7b83ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_d8becf8b-f635-48ef-b6c2-db816dfda776" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_d8becf8b-f635-48ef-b6c2-db816dfda776" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_2cfe1529-bd84-4d06-8f7b-1bdaff55e034" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_2cfe1529-bd84-4d06-8f7b-1bdaff55e034" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_2c49149a-3517-480a-bf49-7a2d138b734a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_2c49149a-3517-480a-bf49-7a2d138b734a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_65a76878-11bd-4b27-a8c5-c2830a849e21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_InventoryNet_65a76878-11bd-4b27-a8c5-c2830a849e21" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_982bc480-0e6f-459a-844b-14a9a487c64c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_982bc480-0e6f-459a-844b-14a9a487c64c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_aad05116-c763-4001-98de-b6ab592d4872" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3cfe14cf-1436-4d68-a6b5-2298ef41d171" xlink:to="loc_us-gaap_AssetsCurrent_aad05116-c763-4001-98de-b6ab592d4872" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_4808ee73-a0e3-4670-9ee0-98c87ebf654e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_4808ee73-a0e3-4670-9ee0-98c87ebf654e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_4529fe45-cf68-4f0f-8a53-59b685745d22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_4529fe45-cf68-4f0f-8a53-59b685745d22" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_70827e5f-a836-4c52-91e9-179f163eaea6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_70827e5f-a836-4c52-91e9-179f163eaea6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_4b86d11a-e50a-4272-a643-495e3d706a8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_4b86d11a-e50a-4272-a643-495e3d706a8a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_c0a7c034-2842-404a-88e3-59791e122372" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_c0a7c034-2842-404a-88e3-59791e122372" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_17cd4dd8-bf4a-4d9f-a548-ade9ea103c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_464d3722-6050-4ceb-9ac6-94ea27129177" xlink:to="loc_us-gaap_Assets_17cd4dd8-bf4a-4d9f-a548-ade9ea103c9a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_85f81a84-da04-48e1-988f-f4afeaf97d27" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_9d94c6d1-095c-4c0b-9c63-29832a72cdb7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_AccountsPayableCurrentAndNoncurrent_9d94c6d1-095c-4c0b-9c63-29832a72cdb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_e46d7c49-bf7a-4865-91d6-7a2294f70c66" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_e46d7c49-bf7a-4865-91d6-7a2294f70c66" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_c276de52-b7fb-42ee-8e12-31be063c584c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_c276de52-b7fb-42ee-8e12-31be063c584c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_824d7539-a35d-4c2a-b970-486303d830c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_824d7539-a35d-4c2a-b970-486303d830c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_98cce575-b02d-4180-9d81-4cca211a3097" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_98cce575-b02d-4180-9d81-4cca211a3097" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_fff20460-2bab-4685-b55c-b0fce4ea290e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_24ca60a1-62eb-43d6-a822-4651bfea1a04" xlink:to="loc_us-gaap_LiabilitiesCurrent_fff20460-2bab-4685-b55c-b0fce4ea290e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_a51415f4-78fa-4917-b8a1-9e50a7286a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_a51415f4-78fa-4917-b8a1-9e50a7286a6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_f73cfd5d-a0bb-401e-a0a7-01dddcbd18a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_f73cfd5d-a0bb-401e-a0a7-01dddcbd18a8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_41854497-8507-47f0-ad52-fd4eb70717c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_Liabilities_41854497-8507-47f0-ad52-fd4eb70717c2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_a412291b-3eae-46a7-a507-764ad6b395fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_CommitmentsAndContingencies_a412291b-3eae-46a7-a507-764ad6b395fc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_5bc68b93-9a96-4469-aa47-2ce0f85bf800" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_PreferredStockValue_5bc68b93-9a96-4469-aa47-2ce0f85bf800" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_fdd52d6b-514f-46c9-8ecc-894c4bdea920" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_CommonStockValue_fdd52d6b-514f-46c9-8ecc-894c4bdea920" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_260248af-f26b-45a2-ad62-e876c5cad418" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_AdditionalPaidInCapital_260248af-f26b-45a2-ad62-e876c5cad418" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_2ec1db05-8ded-49fe-8c36-73d14b4ecc7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_2ec1db05-8ded-49fe-8c36-73d14b4ecc7f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_0dca8efa-94aa-4086-b7d9-da59fb350778" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_0dca8efa-94aa-4086-b7d9-da59fb350778" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b932ce98-7000-4b39-a71b-4544f28e706d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_5225ade9-b9ad-4468-9824-4fd6865034ee" xlink:to="loc_us-gaap_StockholdersEquity_b932ce98-7000-4b39-a71b-4544f28e706d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_ea9b0ce7-0da0-420d-94bd-05818e498bc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9b0c4712-7ac8-4802-adc5-698289ad860e" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_ea9b0ce7-0da0-420d-94bd-05818e498bc3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_bc500226-19c8-4e4c-8536-59cc8bb66f53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_85f81a84-da04-48e1-988f-f4afeaf97d27" xlink:to="loc_us-gaap_StatementTable_bc500226-19c8-4e4c-8536-59cc8bb66f53" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_14a5f587-2f58-4a72-ae21-4635ad6c96b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bc500226-19c8-4e4c-8536-59cc8bb66f53" xlink:to="loc_us-gaap_StatementClassOfStockAxis_14a5f587-2f58-4a72-ae21-4635ad6c96b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_14a5f587-2f58-4a72-ae21-4635ad6c96b0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_14a5f587-2f58-4a72-ae21-4635ad6c96b0" xlink:to="loc_us-gaap_ClassOfStockDomain_14a5f587-2f58-4a72-ae21-4635ad6c96b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_6c0a079e-b191-4fcc-adbe-bd8bd315dcfd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_14a5f587-2f58-4a72-ae21-4635ad6c96b0" xlink:to="loc_us-gaap_ClassOfStockDomain_6c0a079e-b191-4fcc-adbe-bd8bd315dcfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_c42051e6-407f-45ce-b2d3-e7fcdd0a4e56" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_6c0a079e-b191-4fcc-adbe-bd8bd315dcfd" xlink:to="loc_us-gaap_CommonClassAMember_c42051e6-407f-45ce-b2d3-e7fcdd0a4e56" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_f1c9cdcc-48e0-4287-978b-899fa2f4ec82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_6c0a079e-b191-4fcc-adbe-bd8bd315dcfd" xlink:to="loc_us-gaap_CommonClassBMember_f1c9cdcc-48e0-4287-978b-899fa2f4ec82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4a32c278-79e7-46b2-96e4-73de0a8b2093" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bc500226-19c8-4e4c-8536-59cc8bb66f53" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4a32c278-79e7-46b2-96e4-73de0a8b2093" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_4a32c278-79e7-46b2-96e4-73de0a8b2093_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4a32c278-79e7-46b2-96e4-73de0a8b2093" xlink:to="loc_us-gaap_RelatedPartyDomain_4a32c278-79e7-46b2-96e4-73de0a8b2093_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_03017832-6d88-498b-b91c-f0b8dc7aa4f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4a32c278-79e7-46b2-96e4-73de0a8b2093" xlink:to="loc_us-gaap_RelatedPartyDomain_03017832-6d88-498b-b91c-f0b8dc7aa4f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_0e7a63b3-4eb8-4102-acde-08b89700686e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_03017832-6d88-498b-b91c-f0b8dc7aa4f9" xlink:to="loc_us-gaap_NonrelatedPartyMember_0e7a63b3-4eb8-4102-acde-08b89700686e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_b4a035a2-f831-42ca-bda9-613f1db0449a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_03017832-6d88-498b-b91c-f0b8dc7aa4f9" xlink:to="loc_us-gaap_RelatedPartyMember_b4a035a2-f831-42ca-bda9-613f1db0449a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="simple" xlink:href="seer-20230630.xsd#CondensedConsolidatedBalanceSheetsUnauditedParenthetical"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="extended" id="ife578f36e2d24c2da10dfb266464669e_CondensedConsolidatedBalanceSheetsUnauditedParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_a17c478a-f2ef-40ac-9185-9b606c896396" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_a17c478a-f2ef-40ac-9185-9b606c896396" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_f448c7e9-53da-4167-a936-101f02df7d52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_f448c7e9-53da-4167-a936-101f02df7d52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_d16f4f5e-2a54-4667-9030-ab983e61349e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_PreferredStockSharesIssued_d16f4f5e-2a54-4667-9030-ab983e61349e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_4ab943ff-4610-4cf4-95b1-3a92b8d14ce6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_4ab943ff-4610-4cf4-95b1-3a92b8d14ce6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_ffa2d250-7aa8-48b0-bb56-1c6ecc0ec603" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_ffa2d250-7aa8-48b0-bb56-1c6ecc0ec603" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_4ad96caf-fb80-45a8-b6fc-af5be3eface4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_4ad96caf-fb80-45a8-b6fc-af5be3eface4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_98c98aa2-a580-4d89-b886-c7b14d1381cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_CommonStockSharesIssued_98c98aa2-a580-4d89-b886-c7b14d1381cd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_9938587f-6bdc-4970-a4ee-37daea93bd11" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_9938587f-6bdc-4970-a4ee-37daea93bd11" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_cdcd5171-a1f9-4957-a04c-b44239958a07" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ca211825-a306-4075-8e7d-5c240f9aac99" xlink:to="loc_us-gaap_StatementTable_cdcd5171-a1f9-4957-a04c-b44239958a07" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_ada1fb67-b963-416a-8bb3-ce3f6c64e122" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_cdcd5171-a1f9-4957-a04c-b44239958a07" xlink:to="loc_us-gaap_StatementClassOfStockAxis_ada1fb67-b963-416a-8bb3-ce3f6c64e122" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_ada1fb67-b963-416a-8bb3-ce3f6c64e122_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_ada1fb67-b963-416a-8bb3-ce3f6c64e122" xlink:to="loc_us-gaap_ClassOfStockDomain_ada1fb67-b963-416a-8bb3-ce3f6c64e122_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_c1c415cf-42b2-4d17-8ae2-b1ed9129cd0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_ada1fb67-b963-416a-8bb3-ce3f6c64e122" xlink:to="loc_us-gaap_ClassOfStockDomain_c1c415cf-42b2-4d17-8ae2-b1ed9129cd0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_aaaaf127-1b44-476d-8bfb-e711b94b1e54" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_c1c415cf-42b2-4d17-8ae2-b1ed9129cd0e" xlink:to="loc_us-gaap_CommonClassAMember_aaaaf127-1b44-476d-8bfb-e711b94b1e54" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_922d4c06-7324-4e6e-ad9f-ef7690601bba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_c1c415cf-42b2-4d17-8ae2-b1ed9129cd0e" xlink:to="loc_us-gaap_CommonClassBMember_922d4c06-7324-4e6e-ad9f-ef7690601bba" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CondensedConsolidatedStatementsofOperationsandComprehensiveLossUnaudited" xlink:type="simple" xlink:href="seer-20230630.xsd#CondensedConsolidatedStatementsofOperationsandComprehensiveLossUnaudited"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CondensedConsolidatedStatementsofOperationsandComprehensiveLossUnaudited" xlink:type="extended" id="ic732381c41b34fe29176e33f3c37c6e9_CondensedConsolidatedStatementsofOperationsandComprehensiveLossUnaudited">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_e2f85721-62d2-4f55-a100-569e50d3e5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_RevenuesAbstract_e2f85721-62d2-4f55-a100-569e50d3e5fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_7ffac959-8645-4dd6-ae4a-119ed1bb299b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_e2f85721-62d2-4f55-a100-569e50d3e5fb" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_7ffac959-8645-4dd6-ae4a-119ed1bb299b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_cd9cd16a-4ce7-4986-95eb-0abcd2d0c02a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_e2f85721-62d2-4f55-a100-569e50d3e5fb" xlink:to="loc_us-gaap_CostOfRevenue_cd9cd16a-4ce7-4986-95eb-0abcd2d0c02a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_39235fe9-db2f-4e90-870c-8b1367a75d64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_e2f85721-62d2-4f55-a100-569e50d3e5fb" xlink:to="loc_us-gaap_GrossProfit_39235fe9-db2f-4e90-870c-8b1367a75d64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_e6c26905-1093-4bc9-8686-48b57eba0686" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_e6c26905-1093-4bc9-8686-48b57eba0686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_87b1a3d4-49c4-4d29-8967-2ae940e2526c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_e6c26905-1093-4bc9-8686-48b57eba0686" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_87b1a3d4-49c4-4d29-8967-2ae940e2526c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_7e2a0561-643e-473e-b623-a14d39186be1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_e6c26905-1093-4bc9-8686-48b57eba0686" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_7e2a0561-643e-473e-b623-a14d39186be1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_54c2f39b-20ce-4f23-bd11-2bbd08a0e9c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_e6c26905-1093-4bc9-8686-48b57eba0686" xlink:to="loc_us-gaap_OperatingExpenses_54c2f39b-20ce-4f23-bd11-2bbd08a0e9c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_a470e51e-f417-4c87-92d1-b30725ffd133" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_OperatingIncomeLoss_a470e51e-f417-4c87-92d1-b30725ffd133" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_389fbe91-a074-4208-9c03-05fa77308b14" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_389fbe91-a074-4208-9c03-05fa77308b14" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_4f178ea4-fe83-49bb-b424-25fc02192ad3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_389fbe91-a074-4208-9c03-05fa77308b14" xlink:to="loc_us-gaap_InvestmentIncomeInterest_4f178ea4-fe83-49bb-b424-25fc02192ad3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingExpense_4ffd2bda-5f79-4100-a346-5ea0e06f867a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_389fbe91-a074-4208-9c03-05fa77308b14" xlink:to="loc_us-gaap_OtherNonoperatingExpense_4ffd2bda-5f79-4100-a346-5ea0e06f867a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_4ab3956a-3cb8-4839-af80-93ce2b2c0c5b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_389fbe91-a074-4208-9c03-05fa77308b14" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_4ab3956a-3cb8-4839-af80-93ce2b2c0c5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_f7e597da-ae0e-422f-b65e-76a38187a45a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_NetIncomeLoss_f7e597da-ae0e-422f-b65e-76a38187a45a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_0431907a-8ec8-4b2e-922e-1dabcb9bc43f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_0431907a-8ec8-4b2e-922e-1dabcb9bc43f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_f76cd640-f4a1-4353-854b-29e9f16f69c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_f76cd640-f4a1-4353-854b-29e9f16f69c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_54d2e991-283e-4372-bc48-86b47914cf8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_EarningsPerShareBasic_54d2e991-283e-4372-bc48-86b47914cf8d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_4e3f7ca5-b381-44cf-8793-eacf17a986a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_EarningsPerShareDiluted_4e3f7ca5-b381-44cf-8793-eacf17a986a8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e127f69e-28ed-495e-b18f-89e3250fca85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e127f69e-28ed-495e-b18f-89e3250fca85" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_233c91b4-4f47-46a2-9b70-cccec1ae325c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_8893eafa-0323-4d03-92ed-22002ca64031" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_233c91b4-4f47-46a2-9b70-cccec1ae325c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_297ff70b-d964-434e-91c3-82b091d34127" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_bfdb38da-8b42-42c6-9442-315d866483aa" xlink:to="loc_us-gaap_StatementTable_297ff70b-d964-434e-91c3-82b091d34127" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_297ff70b-d964-434e-91c3-82b091d34127" xlink:to="loc_srt_ProductOrServiceAxis_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3" xlink:to="loc_srt_ProductsAndServicesDomain_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_b0d7a782-e5c0-44c0-8c03-8861ba68e8b8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_bdc84f9c-9b0d-46cc-a2a4-1b5b9aa117c3" xlink:to="loc_srt_ProductsAndServicesDomain_b0d7a782-e5c0-44c0-8c03-8861ba68e8b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_0c07c078-fb35-4bf6-8c04-90629dc7cab5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_b0d7a782-e5c0-44c0-8c03-8861ba68e8b8" xlink:to="loc_us-gaap_ProductMember_0c07c078-fb35-4bf6-8c04-90629dc7cab5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_17d9ef9b-721f-416f-8690-7072e2608164" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_b0d7a782-e5c0-44c0-8c03-8861ba68e8b8" xlink:to="loc_us-gaap_ServiceMember_17d9ef9b-721f-416f-8690-7072e2608164" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_GrantAndOtherMember_3ff52cea-a020-4dab-8c76-71843738b03c" xlink:href="seer-20230630.xsd#seer_GrantAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_b0d7a782-e5c0-44c0-8c03-8861ba68e8b8" xlink:to="loc_seer_GrantAndOtherMember_3ff52cea-a020-4dab-8c76-71843738b03c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9adc1164-802b-4d97-861f-9fb536c81cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_297ff70b-d964-434e-91c3-82b091d34127" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9adc1164-802b-4d97-861f-9fb536c81cd9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_9adc1164-802b-4d97-861f-9fb536c81cd9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9adc1164-802b-4d97-861f-9fb536c81cd9" xlink:to="loc_us-gaap_RelatedPartyDomain_9adc1164-802b-4d97-861f-9fb536c81cd9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_34d40403-dd14-45b5-95c5-810287e3d855" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9adc1164-802b-4d97-861f-9fb536c81cd9" xlink:to="loc_us-gaap_RelatedPartyDomain_34d40403-dd14-45b5-95c5-810287e3d855" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_1b8b475e-0d46-4339-a89d-ccd495e309ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_34d40403-dd14-45b5-95c5-810287e3d855" xlink:to="loc_us-gaap_NonrelatedPartyMember_1b8b475e-0d46-4339-a89d-ccd495e309ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_3cd5eaea-b901-4624-8c17-f03ce4f9eebd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_34d40403-dd14-45b5-95c5-810287e3d855" xlink:to="loc_us-gaap_RelatedPartyMember_3cd5eaea-b901-4624-8c17-f03ce4f9eebd" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CondensedConsolidatedStatementsofChangesinStockholdersEquityUnaudited" xlink:type="simple" xlink:href="seer-20230630.xsd#CondensedConsolidatedStatementsofChangesinStockholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CondensedConsolidatedStatementsofChangesinStockholdersEquityUnaudited" xlink:type="extended" id="i32321a0de2454626b5280435b2b1e6a4_CondensedConsolidatedStatementsofChangesinStockholdersEquityUnaudited">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c6b033b0-208c-4a9f-8506-0a732fd0f526" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c6b033b0-208c-4a9f-8506-0a732fd0f526" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_c6da83e7-a330-4502-80b3-51a7ddc202ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_c6da83e7-a330-4502-80b3-51a7ddc202ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_2fc56105-58cf-4c61-a4d0-0ec17fa613c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockholdersEquity_2fc56105-58cf-4c61-a4d0-0ec17fa613c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_1013527b-c765-413c-b945-407e61f34ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_1013527b-c765-413c-b945-407e61f34ba1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_5cd926cc-0bbf-4bd7-8c7f-4f33dcf1c9a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_5cd926cc-0bbf-4bd7-8c7f-4f33dcf1c9a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_f62e092f-6835-4e67-bfd7-124796622df5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_f62e092f-6835-4e67-bfd7-124796622df5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_23436853-9152-407c-a343-a36a6d952096" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_23436853-9152-407c-a343-a36a6d952096" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_9e7b8d3a-5946-4ca1-88c2-b8ca13c74b03" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_9e7b8d3a-5946-4ca1-88c2-b8ca13c74b03" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_8e63dc7d-65ae-4ac4-899f-7dd591616659" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_8e63dc7d-65ae-4ac4-899f-7dd591616659" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_StockIssuedDuringPeriodValueStockOptionsEarlyExercised_10d90dab-bdd6-4882-882f-33f5202a30c8" xlink:href="seer-20230630.xsd#seer_StockIssuedDuringPeriodValueStockOptionsEarlyExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_seer_StockIssuedDuringPeriodValueStockOptionsEarlyExercised_10d90dab-bdd6-4882-882f-33f5202a30c8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_76d2e504-8ce0-49c1-95d1-39593a1aad52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_76d2e504-8ce0-49c1-95d1-39593a1aad52" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6f69d67d-db0b-4fa2-9310-96b5c7f807c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6f69d67d-db0b-4fa2-9310-96b5c7f807c6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_afc77f6d-a9e5-4e05-9cea-81e7cf179ce3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_NetIncomeLoss_afc77f6d-a9e5-4e05-9cea-81e7cf179ce3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_2b01716d-b660-4409-b1e4-9d67fa3a8a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_ed225ec0-737c-4fe4-9269-9858f37df39c" xlink:to="loc_us-gaap_ProfitLoss_2b01716d-b660-4409-b1e4-9d67fa3a8a4c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8e916fe3-2a80-478e-acb0-5c791eb9c8ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4aec2a12-74a3-4504-865c-c1954af8005c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_21cecac9-10c7-462d-9285-99a5d46e4e13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c6b033b0-208c-4a9f-8506-0a732fd0f526" xlink:to="loc_us-gaap_StatementTable_21cecac9-10c7-462d-9285-99a5d46e4e13" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_68370fb0-c19e-43bf-bca0-36555abb1463" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_21cecac9-10c7-462d-9285-99a5d46e4e13" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_68370fb0-c19e-43bf-bca0-36555abb1463" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_68370fb0-c19e-43bf-bca0-36555abb1463_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_68370fb0-c19e-43bf-bca0-36555abb1463" xlink:to="loc_us-gaap_EquityComponentDomain_68370fb0-c19e-43bf-bca0-36555abb1463_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_68370fb0-c19e-43bf-bca0-36555abb1463" xlink:to="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_7fc3bb4c-6010-44c6-86d1-ac18199c7dab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:to="loc_us-gaap_CommonStockMember_7fc3bb4c-6010-44c6-86d1-ac18199c7dab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_5fc4f4c5-37e8-4c59-8191-36345ba66a37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_5fc4f4c5-37e8-4c59-8191-36345ba66a37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_519f00e8-34d2-4bbc-8fe7-e1907e4232da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:to="loc_us-gaap_RetainedEarningsMember_519f00e8-34d2-4bbc-8fe7-e1907e4232da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_71ebac9d-adf2-4b68-97ff-0d2fd2f5238c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e8db699e-ae79-44cf-a120-8978fbfea425" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_71ebac9d-adf2-4b68-97ff-0d2fd2f5238c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CondensedConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="seer-20230630.xsd#CondensedConsolidatedStatementsofCashFlowsUnaudited"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CondensedConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended" id="i2ff125aeb0514f9ab41514af1e4cd861_CondensedConsolidatedStatementsofCashFlowsUnaudited">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b9f0a597-fe97-4462-ae95-9855228cf7a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b9f0a597-fe97-4462-ae95-9855228cf7a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_80059823-996d-4164-bdf1-c4c41483192f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b9f0a597-fe97-4462-ae95-9855228cf7a2" xlink:to="loc_us-gaap_NetIncomeLoss_80059823-996d-4164-bdf1-c4c41483192f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b9f0a597-fe97-4462-ae95-9855228cf7a2" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_aa76f670-0a4d-4e25-8fdf-4c7cc6f9e48a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_ShareBasedCompensation_aa76f670-0a4d-4e25-8fdf-4c7cc6f9e48a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDepreciationAndAmortization_429f8f56-7c11-493e-8aa5-836d34679f4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_OtherDepreciationAndAmortization_429f8f56-7c11-493e-8aa5-836d34679f4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_b39adfbb-61a6-4c9f-bfc4-a2b2eab23776" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_b39adfbb-61a6-4c9f-bfc4-a2b2eab23776" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_04cdf525-c2e8-42d7-9fa0-9428a9d165b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_04cdf525-c2e8-42d7-9fa0-9428a9d165b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_547c28af-bf99-4731-8e76-7b02ee90085e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_InventoryWriteDown_547c28af-bf99-4731-8e76-7b02ee90085e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseExpense_69a6a59e-7c9c-45d1-9933-c86eac9e1c86" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_OperatingLeaseExpense_69a6a59e-7c9c-45d1-9933-c86eac9e1c86" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_ea5a6b0f-ec89-4589-baf6-d7ea59b3b595" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsAndOtherReceivables_ce2f483d-8683-404f-9939-b8f62c1de431" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsAndOtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsAndOtherReceivables_ce2f483d-8683-404f-9939-b8f62c1de431" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2b459dda-6153-457f-92bd-70503c641f57" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2b459dda-6153-457f-92bd-70503c641f57" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_2ad93e34-9370-4a9c-a9d2-4e09534e92cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_2ad93e34-9370-4a9c-a9d2-4e09534e92cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_d85205bf-7db6-4ebc-85c8-c89a0f035a64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_d85205bf-7db6-4ebc-85c8-c89a0f035a64" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_16cc3b39-30d7-4c6c-aba5-5054f1bb6288" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_16cc3b39-30d7-4c6c-aba5-5054f1bb6288" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_IncreaseDecreaseInAccruedAndOtherLiabilities_e5e94055-b385-4905-a07c-3e4a41c3b840" xlink:href="seer-20230630.xsd#seer_IncreaseDecreaseInAccruedAndOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_11bdbe13-e3e2-44bc-bfa9-08a0715334d5" xlink:to="loc_seer_IncreaseDecreaseInAccruedAndOtherLiabilities_e5e94055-b385-4905-a07c-3e4a41c3b840" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_32f016bf-638c-487a-8373-8f1a6565a85c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b9f0a597-fe97-4462-ae95-9855228cf7a2" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_32f016bf-638c-487a-8373-8f1a6565a85c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ff5939b8-0c60-41ab-9487-a0c246266d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ff5939b8-0c60-41ab-9487-a0c246266d4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_25cc5e08-cb52-4cf2-95c9-da9dea219fd0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:to="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_25cc5e08-cb52-4cf2-95c9-da9dea219fd0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_921ff593-b48f-413b-90b8-534f7d7d9988" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:to="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_921ff593-b48f-413b-90b8-534f7d7d9988" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_aa1cee79-8575-41ac-b9ff-4a988b956f82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:to="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_aa1cee79-8575-41ac-b9ff-4a988b956f82" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_9da20c9c-fdcd-48d1-8c92-1d5d4818b337" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d383ece8-cade-42db-a9fd-ebe22aef5c42" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_9da20c9c-fdcd-48d1-8c92-1d5d4818b337" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_93a76080-cc1c-4559-856d-df195f7c12b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_93a76080-cc1c-4559-856d-df195f7c12b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_91e27a32-14cb-4755-83b1-f94d8e71cc06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_91e27a32-14cb-4755-83b1-f94d8e71cc06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_3143c3f8-c82d-428d-ad14-59a129b25051" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_3143c3f8-c82d-428d-ad14-59a129b25051" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_48bed27f-b9a1-4668-b750-b047a55c5098" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_f1418784-7f4f-45c3-a104-c9a4e191077d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_48bed27f-b9a1-4668-b750-b047a55c5098" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_43c09109-835f-401c-931a-62e55f6fdd41" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_43c09109-835f-401c-931a-62e55f6fdd41" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_b61f8fff-465f-44bc-9ca0-ed7f8cd893c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_b61f8fff-465f-44bc-9ca0-ed7f8cd893c5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_3db14399-c1dd-4cb7-9503-6db93cfb3cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_5c0ab0d6-a522-4d8c-90fa-d72ca0cc2f2b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_5c0ab0d6-a522-4d8c-90fa-d72ca0cc2f2b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_30272190-0f26-46ea-a763-39c77363adbd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_5c0ab0d6-a522-4d8c-90fa-d72ca0cc2f2b" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_30272190-0f26-46ea-a763-39c77363adbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTransfersAndChanges_f8585170-69a3-45d5-9366-f321e3001878" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTransfersAndChanges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_5c0ab0d6-a522-4d8c-90fa-d72ca0cc2f2b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTransfersAndChanges_f8585170-69a3-45d5-9366-f321e3001878" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_173e926b-8021-40ed-b0c2-e958affc912f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_5c0ab0d6-a522-4d8c-90fa-d72ca0cc2f2b" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_173e926b-8021-40ed-b0c2-e958affc912f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_7b057e67-9ca0-464a-86de-c322f8dc9106" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c89a2602-3a8d-40b7-a5de-97647861c179" xlink:to="loc_us-gaap_StatementTable_7b057e67-9ca0-464a-86de-c322f8dc9106" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_611d331c-bcfc-4cf8-b646-c1d6736e9f06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7b057e67-9ca0-464a-86de-c322f8dc9106" xlink:to="loc_us-gaap_StatementClassOfStockAxis_611d331c-bcfc-4cf8-b646-c1d6736e9f06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_611d331c-bcfc-4cf8-b646-c1d6736e9f06_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_611d331c-bcfc-4cf8-b646-c1d6736e9f06" xlink:to="loc_us-gaap_ClassOfStockDomain_611d331c-bcfc-4cf8-b646-c1d6736e9f06_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_92e8717f-da2b-4831-938e-056f0747eea6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_611d331c-bcfc-4cf8-b646-c1d6736e9f06" xlink:to="loc_us-gaap_ClassOfStockDomain_92e8717f-da2b-4831-938e-056f0747eea6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_d5f3e083-79cb-4ce3-aa88-9df635e116cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_92e8717f-da2b-4831-938e-056f0747eea6" xlink:to="loc_us-gaap_CommonClassAMember_d5f3e083-79cb-4ce3-aa88-9df635e116cc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/SummaryofSignificantAccountingPoliciesandBasisofPresentationNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#SummaryofSignificantAccountingPoliciesandBasisofPresentationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/SummaryofSignificantAccountingPoliciesandBasisofPresentationNarrativeDetails" xlink:type="extended" id="ic78615f558f442988db4be85d5327c6c_SummaryofSignificantAccountingPoliciesandBasisofPresentationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_008a0f7e-a342-411e-8ac7-93bbd8a0105a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_6af7dafa-8fc8-4497-a44b-27a5f92610cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_008a0f7e-a342-411e-8ac7-93bbd8a0105a" xlink:to="loc_us-gaap_Cash_6af7dafa-8fc8-4497-a44b-27a5f92610cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_ab0c38d5-7727-4314-9279-4775f73b8ca4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_008a0f7e-a342-411e-8ac7-93bbd8a0105a" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_ab0c38d5-7727-4314-9279-4775f73b8ca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_5ce88363-df2a-4b7c-a2fd-07fb68e6da87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_008a0f7e-a342-411e-8ac7-93bbd8a0105a" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_5ce88363-df2a-4b7c-a2fd-07fb68e6da87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_008a0f7e-a342-411e-8ac7-93bbd8a0105a" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_2342aab0-5ec3-4dcb-a94c-62959f757d0a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:to="loc_srt_MajorCustomersAxis_2342aab0-5ec3-4dcb-a94c-62959f757d0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_2342aab0-5ec3-4dcb-a94c-62959f757d0a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_2342aab0-5ec3-4dcb-a94c-62959f757d0a" xlink:to="loc_srt_NameOfMajorCustomerDomain_2342aab0-5ec3-4dcb-a94c-62959f757d0a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_55c12767-fa10-4bb9-83e4-2a7b947381a3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_2342aab0-5ec3-4dcb-a94c-62959f757d0a" xlink:to="loc_srt_NameOfMajorCustomerDomain_55c12767-fa10-4bb9-83e4-2a7b947381a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_MajorCustomer1Member_2461c8f3-f4b7-4cd2-a22f-3b943b5da632" xlink:href="seer-20230630.xsd#seer_MajorCustomer1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_55c12767-fa10-4bb9-83e4-2a7b947381a3" xlink:to="loc_seer_MajorCustomer1Member_2461c8f3-f4b7-4cd2-a22f-3b943b5da632" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_MajorCustomer2Member_b7415d52-80a9-4688-b301-2dfc554911ac" xlink:href="seer-20230630.xsd#seer_MajorCustomer2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_55c12767-fa10-4bb9-83e4-2a7b947381a3" xlink:to="loc_seer_MajorCustomer2Member_b7415d52-80a9-4688-b301-2dfc554911ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_MajorCustomer3Member_f17c685a-658a-47c0-ae06-2c7815743212" xlink:href="seer-20230630.xsd#seer_MajorCustomer3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_55c12767-fa10-4bb9-83e4-2a7b947381a3" xlink:to="loc_seer_MajorCustomer3Member_f17c685a-658a-47c0-ae06-2c7815743212" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_d7f403f3-d974-475a-ad42-7122bc488862" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_d7f403f3-d974-475a-ad42-7122bc488862" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d7f403f3-d974-475a-ad42-7122bc488862_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_d7f403f3-d974-475a-ad42-7122bc488862" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d7f403f3-d974-475a-ad42-7122bc488862_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d309c467-6714-4156-be76-abb2af5028ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_d7f403f3-d974-475a-ad42-7122bc488862" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d309c467-6714-4156-be76-abb2af5028ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_53f9453c-d14d-41e6-93c0-770621be4654" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d309c467-6714-4156-be76-abb2af5028ae" xlink:to="loc_us-gaap_SalesRevenueNetMember_53f9453c-d14d-41e6-93c0-770621be4654" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_15e5cc22-8494-41f8-81fb-dc0146d39e05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d309c467-6714-4156-be76-abb2af5028ae" xlink:to="loc_us-gaap_AccountsReceivableMember_15e5cc22-8494-41f8-81fb-dc0146d39e05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_8512cac9-3b4f-46ed-a488-36143c66287b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_dd5659b1-3ceb-4ac3-91b1-cdafed8a7494" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_8512cac9-3b4f-46ed-a488-36143c66287b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_feb922b8-891d-4992-967f-3417fc08939f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_8512cac9-3b4f-46ed-a488-36143c66287b" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_feb922b8-891d-4992-967f-3417fc08939f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_eccbeea6-6a4d-4baf-86fe-35a4e43a3c63" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_8512cac9-3b4f-46ed-a488-36143c66287b" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_eccbeea6-6a4d-4baf-86fe-35a4e43a3c63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_4a6b337f-de85-49ca-876e-37ee37d28141" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:to="loc_srt_CounterpartyNameAxis_4a6b337f-de85-49ca-876e-37ee37d28141" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_4a6b337f-de85-49ca-876e-37ee37d28141_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_4a6b337f-de85-49ca-876e-37ee37d28141" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_4a6b337f-de85-49ca-876e-37ee37d28141_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6a7e3444-2466-4174-b81b-2e2ecce74294" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_4a6b337f-de85-49ca-876e-37ee37d28141" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6a7e3444-2466-4174-b81b-2e2ecce74294" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_SiliconValleyBankMember_004a24a2-e571-4607-9b41-776db1b990c0" xlink:href="seer-20230630.xsd#seer_SiliconValleyBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6a7e3444-2466-4174-b81b-2e2ecce74294" xlink:to="loc_seer_SiliconValleyBankMember_004a24a2-e571-4607-9b41-776db1b990c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_c01d4792-815e-4a3c-97fb-fbc6f9559caf" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_684d7896-7bf4-4e8b-8edf-64062f07729f" xlink:to="loc_srt_StatementGeographicalAxis_c01d4792-815e-4a3c-97fb-fbc6f9559caf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_c01d4792-815e-4a3c-97fb-fbc6f9559caf_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_c01d4792-815e-4a3c-97fb-fbc6f9559caf" xlink:to="loc_srt_SegmentGeographicalDomain_c01d4792-815e-4a3c-97fb-fbc6f9559caf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_27813624-b9db-43b0-bc72-fec0a145cd4c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_c01d4792-815e-4a3c-97fb-fbc6f9559caf" xlink:to="loc_srt_SegmentGeographicalDomain_27813624-b9db-43b0-bc72-fec0a145cd4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_AsiaAndEuropeMember_ecc9d7fb-5cd1-42a5-97fa-836f532939ee" xlink:href="seer-20230630.xsd#seer_AsiaAndEuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_27813624-b9db-43b0-bc72-fec0a145cd4c" xlink:to="loc_seer_AsiaAndEuropeMember_ecc9d7fb-5cd1-42a5-97fa-836f532939ee" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsFinancialAssetsMeasuredatFairValueOnaRecurringBasisDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#FairValueMeasurementsandFairValueofFinancialInstrumentsFinancialAssetsMeasuredatFairValueOnaRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsFinancialAssetsMeasuredatFairValueOnaRecurringBasisDetails" xlink:type="extended" id="iee6540107b2947c6b3c2ee2fc40598d2_FairValueMeasurementsandFairValueofFinancialInstrumentsFinancialAssetsMeasuredatFairValueOnaRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_97492b71-834a-4aef-865f-96bb1b11389d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_a4b3a275-efc5-4fba-be1c-a9e5d8d5839a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_97492b71-834a-4aef-865f-96bb1b11389d" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_a4b3a275-efc5-4fba-be1c-a9e5d8d5839a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_77af3235-99e3-46cd-9562-6de78fe25cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_97492b71-834a-4aef-865f-96bb1b11389d" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_77af3235-99e3-46cd-9562-6de78fe25cc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_06f684c6-4924-4a13-992d-5b8f1890afa4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_97492b71-834a-4aef-865f-96bb1b11389d" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_06f684c6-4924-4a13-992d-5b8f1890afa4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fc3bcd81-476d-4166-a559-26c1534581ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_97492b71-834a-4aef-865f-96bb1b11389d" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fc3bcd81-476d-4166-a559-26c1534581ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_34ff5c98-399b-430e-a574-a9234f96435e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fc3bcd81-476d-4166-a559-26c1534581ce" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_34ff5c98-399b-430e-a574-a9234f96435e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_34ff5c98-399b-430e-a574-a9234f96435e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_34ff5c98-399b-430e-a574-a9234f96435e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_34ff5c98-399b-430e-a574-a9234f96435e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1b99c030-564d-420e-9c6a-1d7acb2ee7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_34ff5c98-399b-430e-a574-a9234f96435e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1b99c030-564d-420e-9c6a-1d7acb2ee7ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_e8294d87-0c7c-4d1c-b4b7-59fa2d097dff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1b99c030-564d-420e-9c6a-1d7acb2ee7ba" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_e8294d87-0c7c-4d1c-b4b7-59fa2d097dff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_8606061b-e556-4407-9a67-749ca5070e6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1b99c030-564d-420e-9c6a-1d7acb2ee7ba" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_8606061b-e556-4407-9a67-749ca5070e6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_473f448d-a435-4c2c-af5e-d299ec8e50e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1b99c030-564d-420e-9c6a-1d7acb2ee7ba" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_473f448d-a435-4c2c-af5e-d299ec8e50e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_24c101a1-6395-4ddd-b942-368e8e0be8b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fc3bcd81-476d-4166-a559-26c1534581ce" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_24c101a1-6395-4ddd-b942-368e8e0be8b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_24c101a1-6395-4ddd-b942-368e8e0be8b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_24c101a1-6395-4ddd-b942-368e8e0be8b1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_24c101a1-6395-4ddd-b942-368e8e0be8b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_67e7b972-6cd6-4d8b-b1bc-952b4de6daec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_24c101a1-6395-4ddd-b942-368e8e0be8b1" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_67e7b972-6cd6-4d8b-b1bc-952b4de6daec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_77cb970c-93af-41b1-baac-bdd4a667207a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_67e7b972-6cd6-4d8b-b1bc-952b4de6daec" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_77cb970c-93af-41b1-baac-bdd4a667207a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_c3acdfaa-15c5-444a-a4c5-f0d94713a737" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fc3bcd81-476d-4166-a559-26c1534581ce" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_c3acdfaa-15c5-444a-a4c5-f0d94713a737" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_c3acdfaa-15c5-444a-a4c5-f0d94713a737_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_c3acdfaa-15c5-444a-a4c5-f0d94713a737" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_c3acdfaa-15c5-444a-a4c5-f0d94713a737_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_c3acdfaa-15c5-444a-a4c5-f0d94713a737" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_8cf99d87-a4bb-492c-b6c3-cbe37d2043b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:to="loc_us-gaap_MoneyMarketFundsMember_8cf99d87-a4bb-492c-b6c3-cbe37d2043b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_f5489de8-5893-42be-bd5f-1e6501ac798e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_f5489de8-5893-42be-bd5f-1e6501ac798e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_USNonTreasurySecuritiesMember_253b37a4-8d34-460e-81b5-82a8ba722c21" xlink:href="seer-20230630.xsd#seer_USNonTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:to="loc_seer_USNonTreasurySecuritiesMember_253b37a4-8d34-460e-81b5-82a8ba722c21" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_8dcab622-b060-4efb-ae7f-4ded4466f392" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:to="loc_us-gaap_CommercialPaperMember_8dcab622-b060-4efb-ae7f-4ded4466f392" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_3131a6c3-1219-4fd6-a39d-a093e6505e4a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_6fc63713-b3bc-4d06-a925-75f2692fea77" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_3131a6c3-1219-4fd6-a39d-a093e6505e4a" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsUnrealizedGainLossDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#FairValueMeasurementsandFairValueofFinancialInstrumentsUnrealizedGainLossDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsUnrealizedGainLossDetails" xlink:type="extended" id="i6e16406ce8e349069067b3216a0d521e_FairValueMeasurementsandFairValueofFinancialInstrumentsUnrealizedGainLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_afd91b14-db4a-4a6a-93c2-b10d864bd1e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_afd91b14-db4a-4a6a-93c2-b10d864bd1e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_440b5dc6-a7b3-4d50-bb77-5c1d1112bb1e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_440b5dc6-a7b3-4d50-bb77-5c1d1112bb1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_df65d23b-d746-4163-98ae-e3159e54d818" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_df65d23b-d746-4163-98ae-e3159e54d818" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_eb0c4783-ac0e-4af7-94ed-03c9a5ad1b5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_eb0c4783-ac0e-4af7-94ed-03c9a5ad1b5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_aa6b6989-e577-4381-93f6-e5444ac99db2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_ab5de376-1ba6-4b97-9806-7892790c08d5" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_aa6b6989-e577-4381-93f6-e5444ac99db2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_bb28a19e-2afa-440a-a4f3-682241238989" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_aa6b6989-e577-4381-93f6-e5444ac99db2" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_bb28a19e-2afa-440a-a4f3-682241238989" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_bb28a19e-2afa-440a-a4f3-682241238989_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_bb28a19e-2afa-440a-a4f3-682241238989" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_bb28a19e-2afa-440a-a4f3-682241238989_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_5f979320-5058-4ecd-b8a3-8985119ec5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_bb28a19e-2afa-440a-a4f3-682241238989" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_5f979320-5058-4ecd-b8a3-8985119ec5fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsMember_16fec57d-58e2-4be6-965d-0d8e0792e213" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f979320-5058-4ecd-b8a3-8985119ec5fb" xlink:to="loc_us-gaap_CashEquivalentsMember_16fec57d-58e2-4be6-965d-0d8e0792e213" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsMember_fdd5dfad-6db9-416c-9904-d7e568b10723" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f979320-5058-4ecd-b8a3-8985119ec5fb" xlink:to="loc_us-gaap_InvestmentsMember_fdd5dfad-6db9-416c-9904-d7e568b10723" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_aa6b6989-e577-4381-93f6-e5444ac99db2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1ffb8fd5-6d6b-4a95-b0ee-d1727aa5c17d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_1e71e0b4-6827-406c-9d9d-be59ce7ed0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:to="loc_us-gaap_MoneyMarketFundsMember_1e71e0b4-6827-406c-9d9d-be59ce7ed0dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_e3ebbd7e-ba11-4363-8411-9b01ac1167c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_e3ebbd7e-ba11-4363-8411-9b01ac1167c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_USNonTreasurySecuritiesMember_ffbfed00-f979-4a55-a401-568516853c44" xlink:href="seer-20230630.xsd#seer_USNonTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:to="loc_seer_USNonTreasurySecuritiesMember_ffbfed00-f979-4a55-a401-568516853c44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_51f7019d-993d-49b8-a19d-2f0244a88d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:to="loc_us-gaap_CommercialPaperMember_51f7019d-993d-49b8-a19d-2f0244a88d0e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_3ac61cba-69bd-40a2-bf9e-7af9e544c7a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97555477-6224-43d7-8453-d7f41d93eda0" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_3ac61cba-69bd-40a2-bf9e-7af9e544c7a5" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#FairValueMeasurementsandFairValueofFinancialInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/FairValueMeasurementsandFairValueofFinancialInstrumentsNarrativeDetails" xlink:type="extended" id="i620cbc5b7300447f9bd0fee28651a807_FairValueMeasurementsandFairValueofFinancialInstrumentsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_b16be8f7-3210-4276-bc2b-8863a8bcda95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_b16be8f7-3210-4276-bc2b-8863a8bcda95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_d8b5de61-8aa3-4486-9a74-358da42ea84c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_d8b5de61-8aa3-4486-9a74-358da42ea84c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTerm_ebc6b6a1-1438-40a0-b378-56395aff3a8f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTerm_ebc6b6a1-1438-40a0-b378-56395aff3a8f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesFairValueDisclosure_06d5820f-0377-47eb-9b4e-2a1c315aa075" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:to="loc_us-gaap_AccruedLiabilitiesFairValueDisclosure_06d5820f-0377-47eb-9b4e-2a1c315aa075" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_bb9b172b-b026-44ba-8506-de96e17fd56a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1aea48e7-e90f-46d6-aa9a-1bb038b660cf" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_bb9b172b-b026-44ba-8506-de96e17fd56a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fa067bb4-e455-40dc-889c-f89364e1f50e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_bb9b172b-b026-44ba-8506-de96e17fd56a" xlink:to="loc_srt_RangeAxis_fa067bb4-e455-40dc-889c-f89364e1f50e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fa067bb4-e455-40dc-889c-f89364e1f50e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fa067bb4-e455-40dc-889c-f89364e1f50e" xlink:to="loc_srt_RangeMember_fa067bb4-e455-40dc-889c-f89364e1f50e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_1996706d-ca24-4d4d-acc4-06ffa81d7f48" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fa067bb4-e455-40dc-889c-f89364e1f50e" xlink:to="loc_srt_RangeMember_1996706d-ca24-4d4d-acc4-06ffa81d7f48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_e6c80bc6-48cf-4d69-8514-21a10d02e6cb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1996706d-ca24-4d4d-acc4-06ffa81d7f48" xlink:to="loc_srt_MinimumMember_e6c80bc6-48cf-4d69-8514-21a10d02e6cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2d179a07-3cd9-4a21-adc8-3c820cbcce27" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_1996706d-ca24-4d4d-acc4-06ffa81d7f48" xlink:to="loc_srt_MaximumMember_2d179a07-3cd9-4a21-adc8-3c820cbcce27" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/OtherFinancialStatementInformationScheduleofPropertyandEquipmentDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#OtherFinancialStatementInformationScheduleofPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/OtherFinancialStatementInformationScheduleofPropertyandEquipmentDetails" xlink:type="extended" id="ifb4e356b353a43429cbdecd8d4a2ee2d_OtherFinancialStatementInformationScheduleofPropertyandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_3adc28c6-376d-4ca2-996c-6f3b0c387e12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_3adc28c6-376d-4ca2-996c-6f3b0c387e12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_d52447d3-943e-4f2d-b216-446dcfd514a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_d52447d3-943e-4f2d-b216-446dcfd514a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_95f3d73d-4b9a-437d-abfe-153fbe5e31f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_95f3d73d-4b9a-437d-abfe-153fbe5e31f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_4c30822f-e624-4a13-bf65-8a4c02dda90d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:to="loc_us-gaap_Depreciation_4c30822f-e624-4a13-bf65-8a4c02dda90d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b52a0d8-b909-45f1-adfd-c3f404c5c7bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d19d7bca-5840-4cf3-9d6d-2076be673a82" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b52a0d8-b909-45f1-adfd-c3f404c5c7bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4e9907f8-7091-46a4-940c-fbf444d61e82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1b52a0d8-b909-45f1-adfd-c3f404c5c7bc" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4e9907f8-7091-46a4-940c-fbf444d61e82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4e9907f8-7091-46a4-940c-fbf444d61e82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4e9907f8-7091-46a4-940c-fbf444d61e82" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4e9907f8-7091-46a4-940c-fbf444d61e82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4e9907f8-7091-46a4-940c-fbf444d61e82" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_LaboratoryMember_ac3a8194-edbe-4cbf-ba3c-8dd52b0af9b7" xlink:href="seer-20230630.xsd#seer_LaboratoryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:to="loc_seer_LaboratoryMember_ac3a8194-edbe-4cbf-ba3c-8dd52b0af9b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_ComputerEquipmentAndSoftwareMember_9ab93d46-430f-451b-ad9b-10d73c7785c3" xlink:href="seer-20230630.xsd#seer_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:to="loc_seer_ComputerEquipmentAndSoftwareMember_9ab93d46-430f-451b-ad9b-10d73c7785c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_a0e089fd-a2f6-48bf-84a1-d88e251f4500" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_a0e089fd-a2f6-48bf-84a1-d88e251f4500" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_b9a44d50-ea94-4ea9-88c9-7833d50d0f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_b9a44d50-ea94-4ea9-88c9-7833d50d0f3c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_9be94032-91d9-4454-9daf-9d7b6fdc34d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2a881159-bcaf-4d72-9460-906f3819f4fd" xlink:to="loc_us-gaap_ConstructionInProgressMember_9be94032-91d9-4454-9daf-9d7b6fdc34d2" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/RevenueandDeferredRevenueNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#RevenueandDeferredRevenueNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/RevenueandDeferredRevenueNarrativeDetails" xlink:type="extended" id="i40a5c10073ad4cd4b3742e2db03339ac_RevenueandDeferredRevenueNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredRevenueArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_fecb5d1e-e7b8-4033-911e-d2fe03119725" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_fecb5d1e-e7b8-4033-911e-d2fe03119725" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_d0aacc9c-d778-4bab-a259-869f81b3656a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_d0aacc9c-d778-4bab-a259-869f81b3656a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_c0943da1-de77-4ec1-b43d-ec2375551316" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_c0943da1-de77-4ec1-b43d-ec2375551316" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_f40f9036-83f1-4c9a-afec-271cbcf4c289" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_ContractWithCustomerLiability_f40f9036-83f1-4c9a-afec-271cbcf4c289" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c3f3b940-dcd1-4abb-b07d-adc376ee99bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c3f3b940-dcd1-4abb-b07d-adc376ee99bb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredRevenueArrangementByTypeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:to="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fe4d35c7-e979-4221-b062-ec97bbd35a0d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:to="loc_srt_ProductsAndServicesDomain_fe4d35c7-e979-4221-b062-ec97bbd35a0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:to="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrantMember_6d02078a-0dac-41f4-b957-340408578958" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:to="loc_us-gaap_GrantMember_6d02078a-0dac-41f4-b957-340408578958" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:to="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e2d42173-5119-4e44-a21f-2e6388eca67e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e2d42173-5119-4e44-a21f-2e6388eca67e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_NationalInstitutesOfHealthMember_fafc518a-bfa3-4ce3-9bdd-343bb2beb8ed" xlink:href="seer-20230630.xsd#seer_NationalInstitutesOfHealthMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:to="loc_seer_NationalInstitutesOfHealthMember_fafc518a-bfa3-4ce3-9bdd-343bb2beb8ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_a95d69fc-4c9a-4aa0-87f8-e337b41ba7ff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_a95d69fc-4c9a-4aa0-87f8-e337b41ba7ff" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/RevenueandDeferredRevenueNarrativeDetails_1" xlink:type="simple" xlink:href="seer-20230630.xsd#RevenueandDeferredRevenueNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://seer.bio/role/RevenueandDeferredRevenueNarrativeDetails_1" xlink:type="extended" id="ie2bb500e15ec40a88e58feed184c25fe_RevenueandDeferredRevenueNarrativeDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredRevenueArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_fecb5d1e-e7b8-4033-911e-d2fe03119725" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_fecb5d1e-e7b8-4033-911e-d2fe03119725" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_d0aacc9c-d778-4bab-a259-869f81b3656a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_d0aacc9c-d778-4bab-a259-869f81b3656a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_c0943da1-de77-4ec1-b43d-ec2375551316" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_c0943da1-de77-4ec1-b43d-ec2375551316" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_f40f9036-83f1-4c9a-afec-271cbcf4c289" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_ContractWithCustomerLiability_f40f9036-83f1-4c9a-afec-271cbcf4c289" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c3f3b940-dcd1-4abb-b07d-adc376ee99bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_c3f3b940-dcd1-4abb-b07d-adc376ee99bb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredRevenueArrangementByTypeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_949cf793-8ba9-42ee-be8e-be8f981f2362" xlink:to="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:to="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fe4d35c7-e979-4221-b062-ec97bbd35a0d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:to="loc_srt_ProductsAndServicesDomain_fe4d35c7-e979-4221-b062-ec97bbd35a0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_fe4d35c7-e979-4221-b062-ec97bbd35a0d" xlink:to="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrantMember_6d02078a-0dac-41f4-b957-340408578958" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d15ac100-94e4-459f-8db2-aa5ae8cbb9f8" xlink:to="loc_us-gaap_GrantMember_6d02078a-0dac-41f4-b957-340408578958" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_57c8df66-970d-4924-becb-11079e2cb08b" xlink:to="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e2d42173-5119-4e44-a21f-2e6388eca67e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_e2d42173-5119-4e44-a21f-2e6388eca67e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_e2d42173-5119-4e44-a21f-2e6388eca67e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_NationalInstitutesOfHealthMember_fafc518a-bfa3-4ce3-9bdd-343bb2beb8ed" xlink:href="seer-20230630.xsd#seer_NationalInstitutesOfHealthMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d40f8998-3151-4165-88df-170beb9ec07e" xlink:to="loc_seer_NationalInstitutesOfHealthMember_fafc518a-bfa3-4ce3-9bdd-343bb2beb8ed" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CapitalStockandStockholdersEquityNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#CapitalStockandStockholdersEquityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CapitalStockandStockholdersEquityNarrativeDetails" xlink:type="extended" id="i27bc663ddcc04f74ac050989321e008c_CapitalStockandStockholdersEquityNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_78a514c3-ba3b-4ebc-b50c-fe1f6adeb2bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_78a514c3-ba3b-4ebc-b50c-fe1f6adeb2bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_d5987490-dbf1-42a7-b43e-52f4d267bd80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_d5987490-dbf1-42a7-b43e-52f4d267bd80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_641d31c6-d216-4e25-ae6f-cbbd8b03e936" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_641d31c6-d216-4e25-ae6f-cbbd8b03e936" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_CommonStockNumberOfVotes_a5119047-730c-4c0a-b98b-2591d0b123f4" xlink:href="seer-20230630.xsd#seer_CommonStockNumberOfVotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_seer_CommonStockNumberOfVotes_a5119047-730c-4c0a-b98b-2591d0b123f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_87d2748f-bc57-40fb-bc0b-0e08793599d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_87d2748f-bc57-40fb-bc0b-0e08793599d9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_4a98e54d-d4f0-45ad-9b55-8074f4c6699e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_b85a9dcc-ce76-4a17-9bf4-2cf724f6bbc5" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_4a98e54d-d4f0-45ad-9b55-8074f4c6699e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_4a98e54d-d4f0-45ad-9b55-8074f4c6699e" xlink:to="loc_us-gaap_StatementClassOfStockAxis_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7" xlink:to="loc_us-gaap_ClassOfStockDomain_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_03dd464d-e2ea-4088-abeb-4b312f84d98b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_c1ef74fc-567a-44d7-825b-6cf7bedb4fb7" xlink:to="loc_us-gaap_ClassOfStockDomain_03dd464d-e2ea-4088-abeb-4b312f84d98b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_7678afeb-0c13-42cc-9102-ae7ab256cd5c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_03dd464d-e2ea-4088-abeb-4b312f84d98b" xlink:to="loc_us-gaap_CommonClassAMember_7678afeb-0c13-42cc-9102-ae7ab256cd5c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_0e0c8a9d-a7e6-41d3-8976-0f7489fc626a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_03dd464d-e2ea-4088-abeb-4b312f84d98b" xlink:to="loc_us-gaap_CommonClassBMember_0e0c8a9d-a7e6-41d3-8976-0f7489fc626a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/CapitalStockandStockholdersEquityScheduleofCommonStockbyClassDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#CapitalStockandStockholdersEquityScheduleofCommonStockbyClassDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/CapitalStockandStockholdersEquityScheduleofCommonStockbyClassDetails" xlink:type="extended" id="i7518b7f939c44dcc9533d33f58a383d8_CapitalStockandStockholdersEquityScheduleofCommonStockbyClassDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_b88dc23b-5360-4848-a3c6-140a07a4dea7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_39135a57-fa32-4ee9-858f-95f0feefa4eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b88dc23b-5360-4848-a3c6-140a07a4dea7" xlink:to="loc_us-gaap_CommonStockSharesIssued_39135a57-fa32-4ee9-858f-95f0feefa4eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_b8b83cb6-8752-4829-8fb1-3c9be197ee2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_b88dc23b-5360-4848-a3c6-140a07a4dea7" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_b8b83cb6-8752-4829-8fb1-3c9be197ee2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_4a884041-be6c-41cb-8d28-474745e44522" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_b88dc23b-5360-4848-a3c6-140a07a4dea7" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_4a884041-be6c-41cb-8d28-474745e44522" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_15cd3529-62c2-4fab-80ac-f93b521bc603" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_4a884041-be6c-41cb-8d28-474745e44522" xlink:to="loc_us-gaap_StatementClassOfStockAxis_15cd3529-62c2-4fab-80ac-f93b521bc603" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_15cd3529-62c2-4fab-80ac-f93b521bc603_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_15cd3529-62c2-4fab-80ac-f93b521bc603" xlink:to="loc_us-gaap_ClassOfStockDomain_15cd3529-62c2-4fab-80ac-f93b521bc603_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_73f5b25d-a77c-4653-9d7f-f6d80a4ec5e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_15cd3529-62c2-4fab-80ac-f93b521bc603" xlink:to="loc_us-gaap_ClassOfStockDomain_73f5b25d-a77c-4653-9d7f-f6d80a4ec5e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_fe4e07d1-35d2-4e79-9094-c2fab0471ba2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_73f5b25d-a77c-4653-9d7f-f6d80a4ec5e8" xlink:to="loc_us-gaap_CommonClassAMember_fe4e07d1-35d2-4e79-9094-c2fab0471ba2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_1764ccc0-4f91-4179-b41d-de9bfe343e8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_73f5b25d-a77c-4653-9d7f-f6d80a4ec5e8" xlink:to="loc_us-gaap_CommonClassBMember_1764ccc0-4f91-4179-b41d-de9bfe343e8b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/EquityIncentivePlansNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#EquityIncentivePlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/EquityIncentivePlansNarrativeDetails" xlink:type="extended" id="i0733d42f79fe4745b70d0fd483f0949b_EquityIncentivePlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_d6c6e530-2b43-4adf-82cf-b83910fd161b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_d6c6e530-2b43-4adf-82cf-b83910fd161b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_d21a7aa3-e940-47db-89cd-386c4b5672f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_d21a7aa3-e940-47db-89cd-386c4b5672f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_a11e6c19-2eb6-4160-b9c7-02bb17072031" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_SharePrice_a11e6c19-2eb6-4160-b9c7-02bb17072031" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfEachMarketConditionOptionPercent_cea57e6d-c414-4563-9e74-7a24c5cd0d90" xlink:href="seer-20230630.xsd#seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfEachMarketConditionOptionPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfEachMarketConditionOptionPercent_cea57e6d-c414-4563-9e74-7a24c5cd0d90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantDateFairValue_775292c7-9cbd-4d54-b234-d1fdab52ce9b" xlink:href="seer-20230630.xsd#seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantDateFairValue_775292c7-9cbd-4d54-b234-d1fdab52ce9b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketRiskBenefitMeasurementInput_ca3b254c-de70-48cf-9a45-08dc9fa3b1bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketRiskBenefitMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_MarketRiskBenefitMeasurementInput_ca3b254c-de70-48cf-9a45-08dc9fa3b1bb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_21a067fd-f76b-41f1-9312-319b23003fa9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_21a067fd-f76b-41f1-9312-319b23003fa9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_15001763-85d8-434d-82d9-eedf36d02dde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_15001763-85d8-434d-82d9-eedf36d02dde" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_f6b99c60-21cf-4299-be2c-42342a4d2657" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_f6b99c60-21cf-4299-be2c-42342a4d2657" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_db10a3ce-b7f5-40cb-b44c-78e399e11b66" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_db10a3ce-b7f5-40cb-b44c-78e399e11b66" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_84f58359-42e7-4e65-bb13-f9ef7496b92c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_84f58359-42e7-4e65-bb13-f9ef7496b92c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationNumberOfEmployeesAffected_33f20801-896c-4e48-94e2-ae23b97c9b06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationNumberOfEmployeesAffected"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationNumberOfEmployeesAffected_33f20801-896c-4e48-94e2-ae23b97c9b06" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsModificationsToExtendTermAndVestingShares_f4d54d8e-7d57-4646-aa7b-df52b70e3c9a" xlink:href="seer-20230630.xsd#seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsModificationsToExtendTermAndVestingShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_seer_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsModificationsToExtendTermAndVestingShares_f4d54d8e-7d57-4646-aa7b-df52b70e3c9a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue_fe487796-ae48-4c86-b6c8-b0c393817eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue_fe487796-ae48-4c86-b6c8-b0c393817eb9" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_402e3495-146a-45f7-a36a-5dac6bd34309" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_402e3495-146a-45f7-a36a-5dac6bd34309" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_74def7bb-1844-4829-9afe-9b35eb0b4f8f" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1f1f3c5d-f59c-46e4-87df-58c5896d5db0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1f1f3c5d-f59c-46e4-87df-58c5896d5db0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_1f1f3c5d-f59c-46e4-87df-58c5896d5db0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1f1f3c5d-f59c-46e4-87df-58c5896d5db0" xlink:to="loc_us-gaap_ClassOfStockDomain_1f1f3c5d-f59c-46e4-87df-58c5896d5db0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a0d3575f-7843-4b44-a69e-2bc9be53692b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1f1f3c5d-f59c-46e4-87df-58c5896d5db0" xlink:to="loc_us-gaap_ClassOfStockDomain_a0d3575f-7843-4b44-a69e-2bc9be53692b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_df3ca796-b58e-44ca-932a-9fe57a48c96b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a0d3575f-7843-4b44-a69e-2bc9be53692b" xlink:to="loc_us-gaap_CommonClassAMember_df3ca796-b58e-44ca-932a-9fe57a48c96b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_3c797c4c-ff81-4fbf-998f-342481a822a0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:to="loc_us-gaap_PlanNameAxis_3c797c4c-ff81-4fbf-998f-342481a822a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_3c797c4c-ff81-4fbf-998f-342481a822a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_3c797c4c-ff81-4fbf-998f-342481a822a0" xlink:to="loc_us-gaap_PlanNameDomain_3c797c4c-ff81-4fbf-998f-342481a822a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_48be1882-5936-4580-b001-f5ef3f84b856" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_3c797c4c-ff81-4fbf-998f-342481a822a0" xlink:to="loc_us-gaap_PlanNameDomain_48be1882-5936-4580-b001-f5ef3f84b856" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_A2020EquityIncentivePlanMember_465f53f3-1f5e-43d5-a8f9-c5d03bc63aa6" xlink:href="seer-20230630.xsd#seer_A2020EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_48be1882-5936-4580-b001-f5ef3f84b856" xlink:to="loc_seer_A2020EquityIncentivePlanMember_465f53f3-1f5e-43d5-a8f9-c5d03bc63aa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_A2020EmployeeStockPurchasePlanMember_88f31fae-7df8-4747-9515-58f402c02cf1" xlink:href="seer-20230630.xsd#seer_A2020EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_48be1882-5936-4580-b001-f5ef3f84b856" xlink:to="loc_seer_A2020EmployeeStockPurchasePlanMember_88f31fae-7df8-4747-9515-58f402c02cf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_914ecd27-c967-4b04-bbad-1e2a9073790c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:to="loc_us-gaap_AwardTypeAxis_914ecd27-c967-4b04-bbad-1e2a9073790c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_914ecd27-c967-4b04-bbad-1e2a9073790c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_914ecd27-c967-4b04-bbad-1e2a9073790c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_914ecd27-c967-4b04-bbad-1e2a9073790c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_914ecd27-c967-4b04-bbad-1e2a9073790c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_ddf5ed5e-440a-4542-b3d1-5705157462fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:to="loc_us-gaap_StockCompensationPlanMember_ddf5ed5e-440a-4542-b3d1-5705157462fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_MarketConditionOptionsMember_959d76fd-ae9e-44d3-8700-270ea4889e22" xlink:href="seer-20230630.xsd#seer_MarketConditionOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:to="loc_seer_MarketConditionOptionsMember_959d76fd-ae9e-44d3-8700-270ea4889e22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_f625f987-fca1-4018-91df-c4f41deca2f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:to="loc_us-gaap_RestrictedStockMember_f625f987-fca1-4018-91df-c4f41deca2f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_170e6a0d-8dbe-4cb0-9113-b94551c11585" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6f088be4-bc8a-411d-9619-e2cbd0050ae8" xlink:to="loc_us-gaap_EmployeeStockMember_170e6a0d-8dbe-4cb0-9113-b94551c11585" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_1add7304-c869-423f-8897-046dc38f75b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_1add7304-c869-423f-8897-046dc38f75b5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_1add7304-c869-423f-8897-046dc38f75b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_1add7304-c869-423f-8897-046dc38f75b5" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_1add7304-c869-423f-8897-046dc38f75b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_1add7304-c869-423f-8897-046dc38f75b5" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputSharePriceMember_77cdcaa0-a5fb-485b-bf5f-d52cb6b8c40c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputSharePriceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:to="loc_us-gaap_MeasurementInputSharePriceMember_77cdcaa0-a5fb-485b-bf5f-d52cb6b8c40c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_1df9bc68-89db-4443-ad71-cfa3c2c99d44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_1df9bc68-89db-4443-ad71-cfa3c2c99d44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputOptionVolatilityMember_6b82c4d5-02e7-4ffe-a756-a1d9d7b875a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputOptionVolatilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:to="loc_us-gaap_MeasurementInputOptionVolatilityMember_6b82c4d5-02e7-4ffe-a756-a1d9d7b875a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedDividendRateMember_0d94a6f1-eef1-426a-a353-a2a8ba029a84" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputExpectedDividendRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_63eb6fba-6eeb-4b99-8b7c-2dcd3818461a" xlink:to="loc_us-gaap_MeasurementInputExpectedDividendRateMember_0d94a6f1-eef1-426a-a353-a2a8ba029a84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9bc2329b-71e3-4216-947d-76b3f33a70d6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_97c5a932-af8f-4545-891e-99634489ee7c" xlink:to="loc_srt_RangeAxis_9bc2329b-71e3-4216-947d-76b3f33a70d6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9bc2329b-71e3-4216-947d-76b3f33a70d6_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9bc2329b-71e3-4216-947d-76b3f33a70d6" xlink:to="loc_srt_RangeMember_9bc2329b-71e3-4216-947d-76b3f33a70d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_23b96f22-f55d-4b5b-a238-bda4e1560399" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9bc2329b-71e3-4216-947d-76b3f33a70d6" xlink:to="loc_srt_RangeMember_23b96f22-f55d-4b5b-a238-bda4e1560399" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b06c42cf-081f-40fa-b0fa-e60d073079b5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23b96f22-f55d-4b5b-a238-bda4e1560399" xlink:to="loc_srt_MinimumMember_b06c42cf-081f-40fa-b0fa-e60d073079b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_8957db92-df73-45ff-953a-776640bd98bc" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23b96f22-f55d-4b5b-a238-bda4e1560399" xlink:to="loc_srt_MaximumMember_8957db92-df73-45ff-953a-776640bd98bc" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/EquityIncentivePlansRSUActivityforthePeriodDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#EquityIncentivePlansRSUActivityforthePeriodDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/EquityIncentivePlansRSUActivityforthePeriodDetails" xlink:type="extended" id="iba26d742ae7b4a5d81aba3a220ee53ab_EquityIncentivePlansRSUActivityforthePeriodDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b56b3a30-2fc2-4acc-bd8d-b6476bbda978" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b56b3a30-2fc2-4acc-bd8d-b6476bbda978" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_e759f548-20c2-4c80-b6f5-03840f5632c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_e759f548-20c2-4c80-b6f5-03840f5632c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_be54b219-fe3b-44ed-a15e-018fcd7b86ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_be54b219-fe3b-44ed-a15e-018fcd7b86ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_afe0ce75-a77a-47b9-8c80-7ec3eadeca63" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_afe0ce75-a77a-47b9-8c80-7ec3eadeca63" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_0ad9ae49-d45a-4400-885d-621029dfd790" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_26b71c5d-1936-49e3-bb2a-aaf3b71bc87a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_0ad9ae49-d45a-4400-885d-621029dfd790" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_30206829-612f-45ba-9521-b19caf26ab64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b56b3a30-2fc2-4acc-bd8d-b6476bbda978" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_b311fa98-4122-4ada-90d3-0471da4c6932" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_b311fa98-4122-4ada-90d3-0471da4c6932" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_122dabdc-1121-4382-936f-a4c776ee242a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_122dabdc-1121-4382-936f-a4c776ee242a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_cfa702d3-879e-4af7-bf84-9771617298b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_cfa702d3-879e-4af7-bf84-9771617298b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_a9530549-1114-4bb7-950e-433bd14e7254" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_823f26cd-6321-463f-9e8a-f124a406939b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_a9530549-1114-4bb7-950e-433bd14e7254" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_8741c6a0-c7d3-466e-829c-56ba8ae6acf7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a9dd57de-5beb-4595-aaca-50803db48fc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b56b3a30-2fc2-4acc-bd8d-b6476bbda978" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a9dd57de-5beb-4595-aaca-50803db48fc6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_ccedf34a-f97c-41fa-99ed-67958a23cf82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a9dd57de-5beb-4595-aaca-50803db48fc6" xlink:to="loc_us-gaap_AwardTypeAxis_ccedf34a-f97c-41fa-99ed-67958a23cf82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ccedf34a-f97c-41fa-99ed-67958a23cf82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_ccedf34a-f97c-41fa-99ed-67958a23cf82" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ccedf34a-f97c-41fa-99ed-67958a23cf82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1fb2d5cb-a7e3-46f4-ba15-7f1c8f64bc7e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_ccedf34a-f97c-41fa-99ed-67958a23cf82" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1fb2d5cb-a7e3-46f4-ba15-7f1c8f64bc7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_0320a173-3def-4363-94c8-1ef3b3e6004e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1fb2d5cb-a7e3-46f4-ba15-7f1c8f64bc7e" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_0320a173-3def-4363-94c8-1ef3b3e6004e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/EquityIncentivePlansStockBasedCompensationAllocationDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#EquityIncentivePlansStockBasedCompensationAllocationDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/EquityIncentivePlansStockBasedCompensationAllocationDetails" xlink:type="extended" id="i778ced88be3c4b7dbdd81997b6c96c94_EquityIncentivePlansStockBasedCompensationAllocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_7039894c-6169-46e1-b393-5baccc75d213" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_13574ea4-eeea-4530-ac39-f3a1e19fd314" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_7039894c-6169-46e1-b393-5baccc75d213" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_13574ea4-eeea-4530-ac39-f3a1e19fd314" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_a5c31e50-4791-4786-972c-f08389043ed4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_7039894c-6169-46e1-b393-5baccc75d213" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_a5c31e50-4791-4786-972c-f08389043ed4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_fb039491-88d2-4931-8cee-66f4cb14331e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_a5c31e50-4791-4786-972c-f08389043ed4" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_fb039491-88d2-4931-8cee-66f4cb14331e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_fb039491-88d2-4931-8cee-66f4cb14331e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_fb039491-88d2-4931-8cee-66f4cb14331e" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_fb039491-88d2-4931-8cee-66f4cb14331e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ac93ef9c-0ef9-47be-ac61-79334fe98b12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_fb039491-88d2-4931-8cee-66f4cb14331e" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ac93ef9c-0ef9-47be-ac61-79334fe98b12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_2d17a4f1-e485-492c-a142-88feb1472c92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ac93ef9c-0ef9-47be-ac61-79334fe98b12" xlink:to="loc_us-gaap_CostOfSalesMember_2d17a4f1-e485-492c-a142-88feb1472c92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_0ab4fb59-6c0c-4e19-a1f0-ae236743e9c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ac93ef9c-0ef9-47be-ac61-79334fe98b12" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_0ab4fb59-6c0c-4e19-a1f0-ae236743e9c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_6ece9f2f-3fbf-4c7b-9c11-1e468214c569" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ac93ef9c-0ef9-47be-ac61-79334fe98b12" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_6ece9f2f-3fbf-4c7b-9c11-1e468214c569" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/LeasesNarrativeDetails" xlink:type="extended" id="ia9237f2f48384538880f39392d5c215c_LeasesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_LesseeOperatingLeaseNumberOfSquareFeet_9c77b777-e710-41d5-8c86-45c15671258e" xlink:href="seer-20230630.xsd#seer_LesseeOperatingLeaseNumberOfSquareFeet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_seer_LesseeOperatingLeaseNumberOfSquareFeet_9c77b777-e710-41d5-8c86-45c15671258e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorOperatingLeaseRenewalTerm_1b98682e-7acc-4596-8ea5-76eeed7d27ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LessorOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_us-gaap_LessorOperatingLeaseRenewalTerm_1b98682e-7acc-4596-8ea5-76eeed7d27ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_058ecfa0-037a-447f-82cb-ae8fed735fe3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_058ecfa0-037a-447f-82cb-ae8fed735fe3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_acf24b97-5b3d-4916-b9a4-c8c409ad448f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_acf24b97-5b3d-4916-b9a4-c8c409ad448f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_LesseeIncrementalBorrowingRate_53dfb11f-7fd8-4457-8c36-b27787d6a3a5" xlink:href="seer-20230630.xsd#seer_LesseeIncrementalBorrowingRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_seer_LesseeIncrementalBorrowingRate_53dfb11f-7fd8-4457-8c36-b27787d6a3a5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeLeaseRevenue_6975b5b4-ecec-4fbe-ab31-685665ae64d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesTypeLeaseRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_us-gaap_SalesTypeLeaseRevenue_6975b5b4-ecec-4fbe-ab31-685665ae64d9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8867ee12-12b7-417f-a16b-cc0da4c94e9c" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_5b7b2070-f89f-40ff-a357-ebfe20acd4b8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:to="loc_srt_StatementGeographicalAxis_5b7b2070-f89f-40ff-a357-ebfe20acd4b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_5b7b2070-f89f-40ff-a357-ebfe20acd4b8_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_5b7b2070-f89f-40ff-a357-ebfe20acd4b8" xlink:to="loc_srt_SegmentGeographicalDomain_5b7b2070-f89f-40ff-a357-ebfe20acd4b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_5778b3a3-646b-42de-9a43-245b774e46df" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_5b7b2070-f89f-40ff-a357-ebfe20acd4b8" xlink:to="loc_srt_SegmentGeographicalDomain_5778b3a3-646b-42de-9a43-245b774e46df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_RedwoodCityCAMember_05b34f85-645a-4f66-ac89-d3e3c4f5f89d" xlink:href="seer-20230630.xsd#seer_RedwoodCityCAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_5778b3a3-646b-42de-9a43-245b774e46df" xlink:to="loc_seer_RedwoodCityCAMember_05b34f85-645a-4f66-ac89-d3e3c4f5f89d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_SanDiegoCAMember_b8a91333-569b-47e4-82bb-ca4bda3352ec" xlink:href="seer-20230630.xsd#seer_SanDiegoCAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_5778b3a3-646b-42de-9a43-245b774e46df" xlink:to="loc_seer_SanDiegoCAMember_b8a91333-569b-47e4-82bb-ca4bda3352ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_be61025e-32a7-4648-b924-b71d43abb8c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_be61025e-32a7-4648-b924-b71d43abb8c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_be61025e-32a7-4648-b924-b71d43abb8c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_be61025e-32a7-4648-b924-b71d43abb8c7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_be61025e-32a7-4648-b924-b71d43abb8c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8faf0fa1-5bd8-4b8c-8633-89791ed728d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_be61025e-32a7-4648-b924-b71d43abb8c7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8faf0fa1-5bd8-4b8c-8633-89791ed728d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_06fcf9b8-81cb-459d-bbc4-d1438ada7e90" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8faf0fa1-5bd8-4b8c-8633-89791ed728d8" xlink:to="loc_us-gaap_BuildingMember_06fcf9b8-81cb-459d-bbc4-d1438ada7e90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_b1490acf-f17f-4c22-95b0-fea040b1165a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:to="loc_us-gaap_DebtInstrumentAxis_b1490acf-f17f-4c22-95b0-fea040b1165a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b1490acf-f17f-4c22-95b0-fea040b1165a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_b1490acf-f17f-4c22-95b0-fea040b1165a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b1490acf-f17f-4c22-95b0-fea040b1165a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_cf19cb44-26bd-4ef5-a620-a624418620dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_b1490acf-f17f-4c22-95b0-fea040b1165a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_cf19cb44-26bd-4ef5-a620-a624418620dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_FacilityLeaseAgreementLetterOfCreditMember_4f3f5ed6-3223-4cb1-8710-7b09c99fb71b" xlink:href="seer-20230630.xsd#seer_FacilityLeaseAgreementLetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_cf19cb44-26bd-4ef5-a620-a624418620dd" xlink:to="loc_seer_FacilityLeaseAgreementLetterOfCreditMember_4f3f5ed6-3223-4cb1-8710-7b09c99fb71b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_170e2224-953a-443e-aa39-b07ba68025c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_99854fa7-32a1-49c3-9426-c2ef1b9aa7a0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_170e2224-953a-443e-aa39-b07ba68025c8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_170e2224-953a-443e-aa39-b07ba68025c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_170e2224-953a-443e-aa39-b07ba68025c8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_170e2224-953a-443e-aa39-b07ba68025c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_06f489ec-cd2f-4310-b3e8-81090b6e279a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_170e2224-953a-443e-aa39-b07ba68025c8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_06f489ec-cd2f-4310-b3e8-81090b6e279a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_82c4e7b8-48de-4271-9686-4c1f0b49c29f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_06f489ec-cd2f-4310-b3e8-81090b6e279a" xlink:to="loc_us-gaap_LetterOfCreditMember_82c4e7b8-48de-4271-9686-4c1f0b49c29f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/RelatedPartyTransactionsNarrativeDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#RelatedPartyTransactionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/RelatedPartyTransactionsNarrativeDetails" xlink:type="extended" id="ia041581a58544a2b873b01aa3d89176f_RelatedPartyTransactionsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_21c21afb-b7c0-4e87-bb54-49aeaec59ae6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_720a634f-f877-4c98-a23f-37fd77fa9203" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_21c21afb-b7c0-4e87-bb54-49aeaec59ae6" xlink:to="loc_us-gaap_Revenues_720a634f-f877-4c98-a23f-37fd77fa9203" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_f002726b-de8e-47cf-bb64-5a1ca3f06b01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_21c21afb-b7c0-4e87-bb54-49aeaec59ae6" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_f002726b-de8e-47cf-bb64-5a1ca3f06b01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_486a1281-3344-4c59-98d1-1819bf7196d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_21c21afb-b7c0-4e87-bb54-49aeaec59ae6" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_486a1281-3344-4c59-98d1-1819bf7196d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_29909fde-3691-4c25-8b9f-4b9083602360" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_21c21afb-b7c0-4e87-bb54-49aeaec59ae6" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_29909fde-3691-4c25-8b9f-4b9083602360" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3a6d775a-768a-4b50-bf18-410007ad9756" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_29909fde-3691-4c25-8b9f-4b9083602360" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3a6d775a-768a-4b50-bf18-410007ad9756" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_3a6d775a-768a-4b50-bf18-410007ad9756_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3a6d775a-768a-4b50-bf18-410007ad9756" xlink:to="loc_us-gaap_RelatedPartyDomain_3a6d775a-768a-4b50-bf18-410007ad9756_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_828fea88-e942-47f2-a8a2-a218c33c9950" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3a6d775a-768a-4b50-bf18-410007ad9756" xlink:to="loc_us-gaap_RelatedPartyDomain_828fea88-e942-47f2-a8a2-a218c33c9950" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_790fc979-5472-47f3-b69e-63f0450b9cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_828fea88-e942-47f2-a8a2-a218c33c9950" xlink:to="loc_us-gaap_RelatedPartyMember_790fc979-5472-47f3-b69e-63f0450b9cc8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_ccdedfda-e487-4491-8cae-4cf9fb0c955d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_29909fde-3691-4c25-8b9f-4b9083602360" xlink:to="loc_srt_TitleOfIndividualAxis_ccdedfda-e487-4491-8cae-4cf9fb0c955d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ccdedfda-e487-4491-8cae-4cf9fb0c955d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_ccdedfda-e487-4491-8cae-4cf9fb0c955d" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ccdedfda-e487-4491-8cae-4cf9fb0c955d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_441743ee-3afb-4f4e-acdb-af0a35292e45" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_ccdedfda-e487-4491-8cae-4cf9fb0c955d" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_441743ee-3afb-4f4e-acdb-af0a35292e45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveOfficerMember_d29728ce-7979-48c0-b2ff-e9f3e3d73005" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_441743ee-3afb-4f4e-acdb-af0a35292e45" xlink:to="loc_srt_ExecutiveOfficerMember_d29728ce-7979-48c0-b2ff-e9f3e3d73005" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_dff99418-8216-4b98-a32a-acc9616b2405" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_29909fde-3691-4c25-8b9f-4b9083602360" xlink:to="loc_srt_CounterpartyNameAxis_dff99418-8216-4b98-a32a-acc9616b2405" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_dff99418-8216-4b98-a32a-acc9616b2405_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_dff99418-8216-4b98-a32a-acc9616b2405" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_dff99418-8216-4b98-a32a-acc9616b2405_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_88f9c6a2-2b34-45a4-97dd-64280ce2c6d8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_dff99418-8216-4b98-a32a-acc9616b2405" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_88f9c6a2-2b34-45a4-97dd-64280ce2c6d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_seer_PrognomiQMember_f0143dab-edd3-4e35-bd7f-d13282a0d844" xlink:href="seer-20230630.xsd#seer_PrognomiQMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_88f9c6a2-2b34-45a4-97dd-64280ce2c6d8" xlink:to="loc_seer_PrognomiQMember_f0143dab-edd3-4e35-bd7f-d13282a0d844" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/NetLossPerShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#NetLossPerShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/NetLossPerShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesDetails" xlink:type="extended" id="ie8cab831e49a486eaecdf47b8b2bdc75_NetLossPerShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91b0ab3-633d-4c6f-8631-7f2885aa7445" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_11718df6-8c8c-4fdb-8cc2-38d9bcc10f1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91b0ab3-633d-4c6f-8631-7f2885aa7445" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_11718df6-8c8c-4fdb-8cc2-38d9bcc10f1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_715a5953-f194-4ade-97cd-eb204b210e81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91b0ab3-633d-4c6f-8631-7f2885aa7445" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_715a5953-f194-4ade-97cd-eb204b210e81" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3b642ce5-d965-41ce-957c-3bbfc633abff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_715a5953-f194-4ade-97cd-eb204b210e81" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3b642ce5-d965-41ce-957c-3bbfc633abff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3b642ce5-d965-41ce-957c-3bbfc633abff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3b642ce5-d965-41ce-957c-3bbfc633abff" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3b642ce5-d965-41ce-957c-3bbfc633abff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_003b2bfd-5014-4902-82e8-2e4030f43aad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3b642ce5-d965-41ce-957c-3bbfc633abff" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_003b2bfd-5014-4902-82e8-2e4030f43aad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_cfab9669-fcb9-46c6-bb07-a0baa9344bc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_003b2bfd-5014-4902-82e8-2e4030f43aad" xlink:to="loc_us-gaap_EmployeeStockOptionMember_cfab9669-fcb9-46c6-bb07-a0baa9344bc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_56fd89b0-6256-4bcb-a15f-812c0dd70b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_003b2bfd-5014-4902-82e8-2e4030f43aad" xlink:to="loc_us-gaap_RestrictedStockMember_56fd89b0-6256-4bcb-a15f-812c0dd70b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_d8ef7946-068b-47a6-99c1-f38c75d2a281" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_003b2bfd-5014-4902-82e8-2e4030f43aad" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_d8ef7946-068b-47a6-99c1-f38c75d2a281" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://seer.bio/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="seer-20230630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://seer.bio/role/SubsequentEventsDetails" xlink:type="extended" id="ieda86eafa26947599ad77808aab9325c_SubsequentEventsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_d2f05477-ba30-4c00-91a6-0749ce382a07" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent_3b4cc418-586c-4bab-9e2a-012a204403c3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2f05477-ba30-4c00-91a6-0749ce382a07" xlink:to="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent_3b4cc418-586c-4bab-9e2a-012a204403c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_ab2d178b-a2e6-4098-a46b-561623fef6fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2f05477-ba30-4c00-91a6-0749ce382a07" xlink:to="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_ab2d178b-a2e6-4098-a46b-561623fef6fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_862eca14-35b6-407c-ad5a-818b25b84885" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2f05477-ba30-4c00-91a6-0749ce382a07" xlink:to="loc_us-gaap_SubsequentEventTable_862eca14-35b6-407c-ad5a-818b25b84885" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_0442dfb8-fa72-47fc-9480-79423e91a3a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_862eca14-35b6-407c-ad5a-818b25b84885" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_0442dfb8-fa72-47fc-9480-79423e91a3a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_0442dfb8-fa72-47fc-9480-79423e91a3a5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0442dfb8-fa72-47fc-9480-79423e91a3a5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_0442dfb8-fa72-47fc-9480-79423e91a3a5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_a68d76da-5150-4fc3-bcca-bca9fbda0f3d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0442dfb8-fa72-47fc-9480-79423e91a3a5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_a68d76da-5150-4fc3-bcca-bca9fbda0f3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_9ac68f10-8d0e-48d3-83b9-16161118e016" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_a68d76da-5150-4fc3-bcca-bca9fbda0f3d" xlink:to="loc_us-gaap_SubsequentEventMember_9ac68f10-8d0e-48d3-83b9-16161118e016" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_a9b1bca9-cedb-429b-be71-fa1e7774d5d8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_862eca14-35b6-407c-ad5a-818b25b84885" xlink:to="loc_srt_StatementScenarioAxis_a9b1bca9-cedb-429b-be71-fa1e7774d5d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_a9b1bca9-cedb-429b-be71-fa1e7774d5d8_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_a9b1bca9-cedb-429b-be71-fa1e7774d5d8" xlink:to="loc_srt_ScenarioUnspecifiedDomain_a9b1bca9-cedb-429b-be71-fa1e7774d5d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_3730a8ad-be4f-471e-b569-41cfc93c10c9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_a9b1bca9-cedb-429b-be71-fa1e7774d5d8" xlink:to="loc_srt_ScenarioUnspecifiedDomain_3730a8ad-be4f-471e-b569-41cfc93c10c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_483b0817-81e5-471f-950f-24ba1300ec28" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_3730a8ad-be4f-471e-b569-41cfc93c10c9" xlink:to="loc_srt_ScenarioForecastMember_483b0817-81e5-471f-950f-24ba1300ec28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_d44b65c0-7c8c-4152-a166-5ea47d7cea16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_862eca14-35b6-407c-ad5a-818b25b84885" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_d44b65c0-7c8c-4152-a166-5ea47d7cea16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_d44b65c0-7c8c-4152-a166-5ea47d7cea16_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_d44b65c0-7c8c-4152-a166-5ea47d7cea16" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_d44b65c0-7c8c-4152-a166-5ea47d7cea16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_55e9e512-6a2f-4d03-8acc-255d89e3f5fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_d44b65c0-7c8c-4152-a166-5ea47d7cea16" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_55e9e512-6a2f-4d03-8acc-255d89e3f5fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_9096c7dc-31ee-4123-9c55-a611bb3f0840" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_55e9e512-6a2f-4d03-8acc-255d89e3f5fd" xlink:to="loc_us-gaap_EmployeeSeveranceMember_9096c7dc-31ee-4123-9c55-a611bb3f0840" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
