2
underline(verb, strengthen, buttress)
2
vouch(verb, support, back, sign, uphold)
2
warrant(verb, support, back, sign, uphold)
2
witness(verb, support, back, sign, uphold)
1
abide
1
affirm(verb, support, back, sign, uphold)
1
approve(verb, support, back, sign, prove)
1
base(verb, rest, provide, over)
1
bless(verb, support, back, sign, uphold)
1
brook
1
bulwark(hold, reinforce)
1
buy(verb, support, back, sign, uphold)
1
certify(prove, verify, substantiate, validate, corroborate)
1
check(verb, support, back, uphold, explain)
1
check out(expression, prove, verify, substantiate, validate)
1
continue(verb, stay, extend, sustain, last)
1
cradle
1
cushion
1
double-check(verb, support, back, uphold, explain)
1
emphasize(verb, strengthen, buttress)
11 years ago|1.8k views|share |citing 
APASmart Define. (2015). underpin thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/underpin/thesaurus/synonyms
ChicagoSmart Define. 2015. "underpin thesaurus" https://smartdefine.org/underpin/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, underpin thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/underpin/thesaurus/synonyms>.
MLASmart Define. "underpin thesaurus" 10 April 2015. Web. 23 September 2026. <https://smartdefine.org/underpin/thesaurus/synonyms>