11
fateful(adjective, importance, valuable, main, notable)
11
impressive(adjective, importance, valuable, main, notable)
11
influential(adjective, good, great, importance, important)
11
notable(adjective, great, extraordinary, importance, unusual)
11
thoughtful(adjective, severe, deep, sober, thinking)
10
desperate(adjective, severe, significant, extreme, vital)
10
major(adjective, great, unpleasant, heavy, important)
10
outstanding(adjective, great, importance, unusual, important)
10
purposeful(adjective, firm, importance, resolute, valuable)
10
responsible(adjective, importance, valuable, main, notable)
10
steady(adjective, calm, set, cool, firm)
10
stern(adjective, resolute, somber, humorless)
10
terrible(adjective, bad, great, difficult, extraordinary)
9
big-league(adjective, importance, valuable, main, notable)
9
fervent(adjective, complete, keen, warm, total)
9
intense(adjective, severe, keen, warm, sensible)
9
no-nonsense(adjective, calm, dull, work, open)
9
remarkable(adjective, importance, unusual, important, famous)
9
resolute(adjective, severe, firm, sensible, harsh)
9
unsmiling(adjective, somber, humorless)
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APASmart Define. (2016). serious thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 24 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>