12
tense(verb, adjective, hard, strengthen, stiff)
12
thick(adjective, close, strong, hard, tough)
11
abiding(adjective, calm, strong, complete, secure)
11
confirmed(adjective, characteristic, hard, rough, harsh)
11
decisive(adjective, good, set, clear, strong)
10
changeless(adjective, solid, certain, stable, limited)
10
close(adjective, set, fix, hard, settle)
10
exact(adjective, close, correct, severe, plain)
10
immobile(adjective, calm, quiet, strong, secure)
10
immutable(adjective, calm, strong, hard, secure)
10
pertinacious(adjective, strong, tough, determined, steady)
10
set in stone(expression, adjective, idiom, calm, set)
10
single-minded(adjective, tough, solid, intense, deliberate)
10
strong-willed(adjective, strong, tough, intense, deliberate)
10
tireless(adjective, strong, determined, steady, resolute)
10
undeviating(adjective, solid, intense, certain, deliberate)
10
unvarying(adjective, calm, strong, secure, solid)
9
dedicated(adjective, set, clear, strong, tough)
9
earnest(adjective, strong, severe, harsh, important)
9
emphatic(adjective, definite, persistent, unqualified, uncompromising)
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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>