207 entries under hard topic. ×
| obdurate(adjective, strong, secure, tough) | |
| refractory(adjective, strain, rough, harsh) | |
| robust(adjective, strong, sound, complete) | |
| unshakable(adjective, mean, strong, complete) | |
| solid(adjective, calm, good, close, set) | |
| rock-solid(adjective, strain, firmness, compact) | |
| relentless(adjective, mean, strong, tough) | |
| unrelenting(adjective, mean, strong, tough) | |
| adamant(adjective, mean, strong, secure) | |
| tough(adjective, calm, mean, clear, strong) | |
| obstinate(adjective, mean, strong, tough) | |
| sturdy(adjective, calm, strong, sound) | |
| secure(verb, adjective, calm, fix, strong) | |
| dogged(adjective, mean, strong, tough) | |
| adamantine(adjective, strong, tough, determined) | |
| dense(adjective, set, strong, tough) | |
| strict(adjective, close, strong, tough) | |
| iron(noun, adjective, mean, strong) | |
| rooted(adjective, strong, secure, property) | |
| compact(verb, adjective, close, set, fix) |
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| APA | Smart Define. (2016). firm thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/firm/thesaurus/synonyms |
| Chicago | Smart Define. 2016. "firm thesaurus" https://smartdefine.org/firm/thesaurus/synonyms (accessed September 24, 2026). |
| Harvard | Smart Define 2016, firm thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/firm/thesaurus/synonyms>. |
| MLA | Smart Define. "firm thesaurus" 31 March 2016. Web. 24 September 2026. <https://smartdefine.org/firm/thesaurus/synonyms> |