222 entries under tough topic. ×
| abiding(adjective, calm, strong, complete, secure) | |
| pertinacious(adjective, strong, determined, steady) | |
| set in stone(expression, adjective, idiom, calm, set) | |
| single-minded(adjective, solid, intense, deliberate) | |
| strong-willed(adjective, strong, intense, deliberate) | |
| dedicated(adjective, set, clear, strong) | |
| flinty(adjective, strong, hard, severe) | |
| implacable(adjective, mean, strong, hard) | |
| indomitable(adjective, strong, hard, determined) | |
| hardy(noun, adjective, strong, sound) | |
| heavy(adjective, set, strong, hard, sound) | |
| indefatigable(adjective, strong, fit, solid) | |
| purposeful(adjective, strong, determined, serious) | |
| rugged(adjective, set, strong, hard, sound) | |
| bound(adjective, set, strong, intense) | |
| brave(adjective, clear, severe, determined) | |
| callous(verb, adjective, close, set, fix) | |
| intractable(adjective, persistent, rigid, inflexible) | |
| mulish(adjective, mean, strong, hard) | |
| rigorous(adjective, strong, hard, complete) |
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| APA | Smart Define. (2016). firm thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/firm/thesaurus/synonyms |
| Chicago | Smart Define. 2016. "firm thesaurus" https://smartdefine.org/firm/thesaurus/synonyms (accessed September 29, 2026). |
| Harvard | Smart Define 2016, firm thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/firm/thesaurus/synonyms>. |
| MLA | Smart Define. "firm thesaurus" 31 March 2016. Web. 29 September 2026. <https://smartdefine.org/firm/thesaurus/synonyms> |