97 entries under thoughtful topic. ×

8
ruminative(adjective, reasonable, rational, sober)
8
somber(adjective, calm, dull, cool, severe)
7
pensive(adjective, set, keen, unhappy, gloomy)
7
austere(adjective, set, strong, hard, tough)
7
genuine(adjective, set, open, honest, total)
6
deliberate(adjective, calm, set, cool, severe)
6
reflective(adjective, set, deep, sober)
6
resolved(adjective, severe, firm, harsh, cruel)
4
contemplative(adjective, reasonable, sober, thinking)
4
meditative(adjective, set, thinking, stern)
4
set(adjective, strong, severe, firm)
3
careful(adjective, regular, practical, competent)
3
cogitative(adjective, reasonable, keen, deep)
3
diligent(adjective, resolute, practical, controlled)
3
musing(adjective, reasonable, keen, deep)
3
quiet(adjective, calm, cool, severe, gentle)
3
thorough(adjective, deep, resolute, practical)
3
wistful(adjective, reasonable, keen, unhappy, gloomy)
2
abstruse(intense, heavy, deep, fierce)
2
assiduous(adjective, reflective)
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APASmart Define. (2016). serious thesaurus. Retrieved September 28, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 28, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 28 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 28 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>