36
rock-solid(adjective, hard, strain, firmness, compact)
35
relentless(adjective, mean, strong, hard, tough)
34
unrelenting(adjective, mean, strong, hard, tough)
32
adamant(adjective, mean, strong, hard, secure)
31
tough(adjective, calm, mean, clear, strong)
30
staunch(noun, adjective, calm, good, close)
29
loyal(adjective, good, close, strong, correct)
29
obstinate(adjective, mean, strong, hard, tough)
29
resolved(adjective, set, severe, harsh, certain)
29
tenacious(adjective, clear, strong, sound, free)
28
sturdy(adjective, calm, strong, hard, sound)
26
unfaltering(adjective, strong, complete, total, solid)
24
secure(verb, adjective, calm, fix, strong)
24
unflinching(adjective, strong, certain, determined, steady)
23
unswerving(adjective, close, strong, tough, correct)
22
sure(adjective, calm, good, close, clear)
21
company(noun, organization, business, person, group)
21
decided(adjective, set, clear, intense, certain)
21
dogged(adjective, mean, strong, hard, tough)
21
established(adjective, definite, strong, state, calm)
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APASmart Define. (2016). firm thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/firm/thesaurus/synonyms
ChicagoSmart Define. 2016. "firm thesaurus" https://smartdefine.org/firm/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, firm thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/firm/thesaurus/synonyms>.
MLASmart Define. "firm thesaurus" 31 March 2016. Web. 22 September 2026. <https://smartdefine.org/firm/thesaurus/synonyms>