207 entries under hard topic. ×

8
condensed(adjective, set, solid, heavy)
8
heavy(adjective, set, strong, sound)
8
rugged(adjective, set, strong, sound)
7
callous(verb, adjective, close, set, fix)
7
hanging tough(expression, adjective, mean, determined)
7
indurate(verb, adjective, close, set, fix)
7
mulish(adjective, mean, strong, tough)
7
rigorous(adjective, strong, complete, tough)
6
grim(adjective, strong, tough, severe)
6
harsh(adjective, mean, strong, tough)
6
headstrong(adjective, tough, rough, harsh)
6
impervious(adjective, set, strong, tough)
6
steadfastly(adverb, fast, severely, thoroughly)
6
unbreakable(adjective, strong, tough, severe)
5
consolidated(adjective, close, set, solid)
5
hardened(adjective, set, strong, tough)
5
impermeable(adjective, close, solid, fast)
5
ironclad(adjective, set, usual, regular)
5
petrified(adjective, calm, set, strong)
5
rocky(adjective, set, strong, difficult)
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APASmart Define. (2016). firm thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/firm/thesaurus/synonyms
ChicagoSmart Define. 2016. "firm thesaurus" https://smartdefine.org/firm/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, firm thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/firm/thesaurus/synonyms>.
MLASmart Define. "firm thesaurus" 31 March 2016. Web. 25 September 2026. <https://smartdefine.org/firm/thesaurus/synonyms>