most serious

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somber, humorless adj.
crucial, weighty adj.

ADJECTIVE

somber, humorless

Synonyms

STRONGEST

deliberate genuine honest severe sincere thoughtful

STRONG

sober

WEAK

austere bound bound and determined businesslike cold sober contemplative deadpan determined downbeat earnest funereal go for broke grave grim intent long-faced meditative no-nonsense pensive pokerfaced reflective resolute resolved sedate set solemn staid steady stern unhumorous unsmiling weighty

Antonyms

STRONGEST

deceptive dishonest false insincere misleading untrustworthy

WEAK

flippant funny happy light minor trivial unimportant unserious

ADJECTIVE

crucial, weighty

Synonyms

STRONGEST

dangerous deep difficult far-reaching grievous important major meaningful severe significant tough urgent

WEAK

arduous fateful fell formidable grave grim hard heavy laborious meaning business menacing momentous no joke no laughing matter of consequence operose out for blood playing hard ball pressing smoking sobering strenuous strictly business threatening ugly unamusing unhumorous worrying

Antonyms

STRONGEST

calm easy facile friendly insignificant little meaningless minor small trivial unimportant worthless

WEAK

flippant funny happy light unserious

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

most serious

It is among the most serious illnesses a woman can experience after giving birth, experts told the BBC, but it remains unclassified in medicine's encyclopaedia of psychiatry.

From BBC ● Aug. 19, 2026

Starlink’s most serious competitor in rural and suburban areas is 5G home internet, according to Cooper.

From MarketWatch ● Aug. 7, 2026

The most serious Medicaid fraud was generally committed by healthcare providers and contractors, not patients.

From Salon ● Aug. 5, 2026

Aedes mosquitoes are vectors for some of the most serious and widespread mosquito-borne diseases.

From Slate ● Aug. 4, 2026

This sounded serious, so I put on my most serious, problem-solving face.

From "The World According to Humphrey" by Betty G. Birney