118 entries under significant topic. ×
| grave(adjective, calm, dull, quiet, help) | |
| weighty(adjective, good, dull, hard, great) | |
| important(adjective, good, great, severe, extraordinary) | |
| earnest(noun, adjective, calm, dull, work) | |
| critical(adjective, hard, great, tough, severe) | |
| difficult(adjective, hard, tough, easy, harsh) | |
| grievous(adjective, help, hard, great, tough) | |
| momentous(adjective, good, great, severe, extraordinary) | |
| consequential(adjective, good, harsh, importance, big) | |
| tough(adjective, bad, strong, hard, easy) | |
| hard(adjective, strong, tough, easy, severe) | |
| arduous(adjective, hard, tough, easy, difficult) | |
| laborious(adjective, hard, easy, difficult, important) | |
| operose(adjective, hard, difficult, important, complex) | |
| heavy(adjective, strong, hard, great, tough) | |
| vital(adjective, great, severe, importance, big) | |
| substantial(adjective, importance, big, heavy, important) | |
| pressing(adjective, hard, tough, difficult, big) | |
| dangerous(adjective, help, bad, great, severe) | |
| crucial(adjective, great, severe, extraordinary, big) |
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| APA | Smart Define. (2016). serious thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/serious/thesaurus/synonyms |
| Chicago | Smart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 23, 2026). |
| Harvard | Smart Define 2016, serious thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>. |
| MLA | Smart Define. "serious thesaurus" 24 February 2016. Web. 23 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms> |