275 entries under solid topic. ×

8
compressed(adjective, set, hard, heavy)
8
concentrated(adjective, set, strong, hard)
8
condensed(adjective, set, hard, heavy)
8
hardy(noun, adjective, strong, sound, tough)
8
heavy(adjective, set, strong, hard, sound)
8
indefatigable(adjective, strong, tough, fit)
8
rugged(adjective, set, strong, hard, sound)
7
indurate(verb, adjective, close, set, fix)
7
unflagging(adjective, strong, tough, fit)
7
vigorous(adjective, strong, tough, fit)
6
harden(verb, close, set, settle)
6
impervious(adjective, set, strong, hard, tough)
6
pat(adjective, determined, usual, steady)
6
powerful(adjective, strong, sound, tough, fit)
6
trusty(adjective, good, close, strong, correct)
6
unbreakable(adjective, strong, hard, tough, severe)
5
absolute(adjective, clear, strong, complete, easy)
5
balanced(adjective, calm, strong, secure, easy)
5
consolidated(adjective, close, set, hard)
5
hardened(adjective, set, strong, hard, tough)
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APASmart Define. (2016). firm thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/firm/thesaurus/synonyms
ChicagoSmart Define. 2016. "firm thesaurus" https://smartdefine.org/firm/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2016, firm thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/firm/thesaurus/synonyms>.
MLASmart Define. "firm thesaurus" 31 March 2016. Web. 23 September 2026. <https://smartdefine.org/firm/thesaurus/synonyms>