122 entries under hard topic. ×
| sensitive(adjective, difficult, complex) | |
| sophisticated(adjective, difficult, complex) | |
| sticky(adjective, difficult, complex, awkward) | |
| toilful(adjective, difficult, complex, awkward) | |
| toilsome(adjective, difficult, harsh, cruel) | |
| hefty(adjective, difficult, complex) | |
| messy(adjective, difficult, unpleasant, complex) | |
| taxing(adjective, difficult, complex) | |
| tricky(adjective, difficult, complex, awkward) | |
| trying(adjective, difficult, complex) | |
| unbearable(adjective, difficult, complex) | |
| pressing(adjective, tough, difficult, big) | |
| urgent(adjective, tough, severe, difficult) | |
| challenging(adjective, tough, difficult, importance) | |
| dour(adjective, close, severe, harsh) | |
| austere(adjective, set, strong, tough) | |
| formidable(adjective, bad, difficult, unpleasant) | |
| strenuous(adjective, severe, rough, difficult) | |
| firm(adjective, strong, tough, severe) | |
| relentless(adjective, close, strong, tough) |
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| APA | Smart Define. (2016). serious thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/serious/thesaurus/synonyms |
| Chicago | Smart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 26, 2026). |
| Harvard | Smart Define 2016, serious thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>. |
| MLA | Smart Define. "serious thesaurus" 24 February 2016. Web. 26 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms> |