5
funereal(adjective, dull, dark, gloomy, sober)
5
gloomy(adjective, dull, unhappy, dark, unpleasant)
5
imposing(importance, grand, esteemed, respected, august)
5
life-and-death(adjective, heavy, important, critical, vital)
5
loyal(adjective, resolute)
5
main(significant, basic, prime, vital, imperative)
5
noteworthy(adjective, important, outstanding, prominent, remarkable)
5
parlous(adjective, dangerous)
5
passionate(adjective, complete, keen, warm, total)
5
saturnine(adjective, severe, unpleasant, horrible, disagreeable)
5
strenuous(adjective, hard, severe, rough, difficult)
4
contemplative(adjective, reasonable, thoughtful, sober, thinking)
4
burning(adjective, keen, warm, intense, passionate)
4
classical
4
collected(adjective, calm, cool, dark, relaxed)
4
cool(adjective, calm, sensible, unusual, relaxed)
4
decided(adjective, strong, firm, determined, resolute)
4
distinguished(adjective, great, unusual, important, famous)
4
drab(adjective, calm, dull, sensible, dark)
4
estimable(adjective, honest, pure, straight, grand)
10 years ago|45k views|share |citing 
APASmart Define. (2016). serious thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 23 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>