918 entries under adjective topic. ×

4
fell(unpleasant, heavy, important, significant)
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fervid(keen, intense, passionate, enthusiastic)
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firm(strong, hard, tough, severe)
4
formal
4
full
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grim-faced
4
grim-visaged
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gross(bad, offensive, foul, obvious)
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honorable(honest, straight, grand, upright)
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hot(great, keen, warm, intense)
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long-faced(somber, dejection, humorless)
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majestic
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meditative(set, thoughtful, thinking, stern)
4
no joke(expression, idiom, dullness, weighty)
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no laughing matter(expression, idiom, weighty, aper)
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persevering(strong, firm, determined, resolute)
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persistent(strong, firm, determined, bold)
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real(open, warm, honest, total)
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relentless(close, strong, hard, tough)
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rigid(strong, hard, tough, severe)
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APASmart Define. (2016). serious thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 27 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>