118 entries under significant topic. ×

7
relevant(adjective, importance, big, substantial)
6
formidable(adjective, bad, hard, difficult, unpleasant)
6
menacing(adjective, bad, nasty, unpleasant, heavy)
6
noble(adjective, importance, important, grand)
6
threatening(adjective, bad, severe, unpleasant, heavy)
6
ugly(adjective, bad, nasty, offensive, unpleasant)
5
main(basic, prime, vital, imperative)
5
strenuous(adjective, hard, severe, rough, difficult)
4
distinguished(adjective, great, unusual, important, famous)
4
fell(adjective, unpleasant, heavy, important)
4
firm(adjective, strong, hard, tough, severe)
4
hot(adjective, great, keen, warm, intense)
4
strong(adjective, hard, tough, firm, solid)
3
capital(adjective, severe, important, critical)
3
central(adjective, important, basic, prime)
3
goodly(large, greatness, considerable)
3
major-league(adjective, great, extraordinary, unusual, important)
3
powerful(adjective, good, important, prominent)
3
prominent(adjective, good, great, unusual, important)
3
sound(adjective, calm, strong, honest, solid)
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APASmart Define. (2016). serious thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 26, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 26 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>