90 entries under straightforward topic. ×

37
earnest(noun, adjective, calm, dull, work)
30
sober(adjective, calm, dull, quiet, cool)
15
sincere(noun, adjective, open, keen, warm)
9
no-nonsense(adjective, calm, dull, work, open)
8
honest(adjective, set, open, true, natural)
7
genuine(adjective, set, open, honest, total)
6
heartfelt(adjective, open, keen, warm, honest)
6
wholehearted(adjective, open, keen, warm, honest)
5
calm(adjective, cool, tough, sensible, relaxed)
5
devout(adjective, open, keen, warm, honest)
4
faithful(adjective, open, firm, honest, true)
4
real(adjective, open, warm, honest, total)
4
true(adjective, strong, open, warm, firm)
3
dear(adjective, open, honest, true)
3
dull(adjective, tough, severe, dark, gloomy)
3
practical(adjective, calm, tough, plain, dark)
3
sensible(adjective, calm, relaxed, pure, rational)
2
deadpan(adjective, set, tough, severe, honest)
2
impassive(adjective, calm, tough, restrained, rational)
2
rational(adjective, calm, reasonable, keen, dark)
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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>