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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a0d530-d414-746e-9b7f-2c904f1c78c8,g:f90ab2c5-966e-42a8-a341-5e09579a40b4-->
<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://www.hyliion.com/role/Cover" xlink:type="simple" xlink:href="hyln-20260928.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.hyliion.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_01a0f93d-0347-7b66-843d-b46438b7cc57" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_01a0f93d-0347-780b-b120-8219f413c2fb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_01a0f93d-0347-7b66-843d-b46438b7cc57" xlink:to="loc_dei_DocumentInformationTable_01a0f93d-0347-780b-b120-8219f413c2fb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_01a0f93d-0347-7d0e-801b-a169a0f664ac" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingsExchangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_01a0f93d-0347-780b-b120-8219f413c2fb" xlink:to="loc_dei_EntityListingsExchangeAxis_01a0f93d-0347-7d0e-801b-a169a0f664ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_01a0f93d-0347-7d0e-801b-a169a0f664ac_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityListingsExchangeAxis_01a0f93d-0347-7d0e-801b-a169a0f664ac" xlink:to="loc_dei_ExchangeDomain_01a0f93d-0347-7d0e-801b-a169a0f664ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_01a0f93d-0347-75cd-beb4-b94c203b8d04" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityListingsExchangeAxis_01a0f93d-0347-7d0e-801b-a169a0f664ac" xlink:to="loc_dei_ExchangeDomain_01a0f93d-0347-75cd-beb4-b94c203b8d04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_exch_XASE_01a0f940-3d9a-7dc1-b06a-038aacd8e7a1" xlink:href="https://xbrl.sec.gov/exch/2026/exch-2026.xsd#exch_XASE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_01a0f93d-0347-75cd-beb4-b94c203b8d04" xlink:to="loc_exch_XASE_01a0f940-3d9a-7dc1-b06a-038aacd8e7a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_exch_XCHI_01a0f942-012a-7bb7-adee-3e3b33fa1898" xlink:href="https://xbrl.sec.gov/exch/2026/exch-2026.xsd#exch_XCHI"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_01a0f93d-0347-75cd-beb4-b94c203b8d04" xlink:to="loc_exch_XCHI_01a0f942-012a-7bb7-adee-3e3b33fa1898" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_01a0f93d-0347-789c-9058-884e1c247dab" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a0f93d-0347-7b66-843d-b46438b7cc57" xlink:to="loc_dei_SecurityExchangeName_01a0f93d-0347-789c-9058-884e1c247dab" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
