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Definitions

serious

[seer-ee-uhs] / ˈsɪər i əs /
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.

He does seem serious about the venture, is hiring for it and gathering chip-making partners.

From The Wall Street Journal • Apr. 24, 2026

Olaf's role is to investigate allegations of fraud that relate to the EU's budget, as well as corruption and serious misconduct within EU institutions.

From BBC • Apr. 24, 2026

Lightning, one of more than 100 robots running the Beijing E-Town, avoided a serious mishap and crossed the finish line in a record 50 minutes, 26 seconds.

From Los Angeles Times • Apr. 23, 2026

Applicants also have to pay a $15,000 Department of Homeland Security processing fee, and Lutnick said they would go through a "most serious vetting and analysis."

From Barron's • Apr. 23, 2026

“Black and white, orange beak, my size, more or less. Has wings— that’s important. And a marcher. Ooh, yes, very serious about his marching. I’m taking lessons!”

From "The Very, Very Far North" by Dan Bar-el

Vocabulary lists containing serious

The SAT: Words to Capture Tone, List 3

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The SAT: Multiple-Meaning Words, List 5

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

The New SAT: Words to Capture Tone

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!