222 entries under tough topic. ×
| unflagging(adjective, strong, fit, solid) | |
| vigorous(adjective, strong, fit, solid) | |
| grim(adjective, strong, hard, severe) | |
| harsh(adjective, mean, strong, hard) | |
| headstrong(adjective, hard, rough, harsh) | |
| impervious(adjective, set, strong, hard) | |
| powerful(adjective, strong, sound, fit) | |
| recalcitrant(adjective, persistent, obstinate, stubborn) | |
| unbreakable(adjective, strong, hard, severe) | |
| contumacious(adjective, persistent, obstinate, stubborn) | |
| hardened(adjective, set, strong, hard) | |
| incompliant(adjective, solid, determined, stiff) | |
| austere(adjective, strong, hard, severe) | |
| healthy(adjective, strong, sound, complete) | |
| hearty(adjective, strong, sound, complete) | |
| insubordinate(adjective, persistent, obstinate, stubborn) | |
| potent(adjective, clear, strong, sound) | |
| serious(adjective, strong, hard, severe) | |
| stiff-necked(adjective, mean, strong, hard) | |
| uncompliant(adjective, determined, resolute, stubborn) |
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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> |