100 entries under restrained topic. ×

3
imperturbable(adjective, calm, cool, sensible, dark)
3
practical(adjective, calm, tough, plain, dark)
3
quiet(adjective, calm, cool, severe, gentle)
3
reasonable(adjective, calm, keen, sensible)
3
sound(adjective, calm, strong, honest, solid)
2
aloof(adjective, calm, subdued, impassive)
2
crestfallen(quiet, gentle)
2
dejected(quiet, gentle)
2
downcast(quiet, gentle)
2
impassive(adjective, calm, tough, rational)
2
rational(adjective, calm, reasonable, keen, dark)
2
realistic(adjective, calm, tough, sensible, dark)
2
reserved(adjective, calm, sensible, modest)
1
abstaining(adjective, calm, sensible, dark)
1
chastened(quiet, gentle)
1
clear-headed(adjective, calm, sensible, dark)
1
cold(adjective, calm, close, hard, tough)
1
dim(adjective, dull, quiet, gentle, dark)
1
disciplined(adjective, calm, sensible, alert)
1
dispassionate(adjective, calm, cool, relaxed)
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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>