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Synonyms

serious

American  
[seer-ee-uhs] / ˈsɪər i əs /

adjective

  1. of, showing, or characterized by deep thought.

  2. of grave or somber disposition, character, or manner.

    a serious occasion; a serious man.
    Synonyms:
    staid, sedate, sober

  3. being in earnest; sincere; not trifling.

    His interest was serious.
    Antonyms:
    trifling, frivolous

  4. requiring thought, concentration, or application.

    serious reading; a serious task.

  5. weighty or important.

    a serious book; Marriage is a serious matter.
    Synonyms:
    grave, momentous
    Antonyms:
    trivial

  6. giving cause for apprehension; critical.

    The plan has one serious flaw.

  7. Medicine/Medical. (of a patient's condition) having unstable or otherwise abnormal vital signs and other unfavorable indicators, as loss of appetite and poor mobility: patient is acutely ill.

noun

  1. that which is of importance, grave, critical, or somber.

    You have to learn to separate the serious from the frivolous.
serious British  
/ ˈsɪərɪəs /

adjective

  1. grave in nature or disposition; thoughtful

    a serious person

  2. marked by deep feeling; in earnest; sincere

    is he serious or joking?

  3. concerned with important matters

    a serious conversation

  4. requiring effort or concentration

    a serious book

  5. giving rise to fear or anxiety; critical

    a serious illness

  6. informal worthy of regard because of substantial quantity or quality

    serious money

    serious wine

  7. informal extreme or remarkable

    a serious haircut
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Related Words

See earnest 1.

Other Word Forms

  • half-serious adjective
  • half-seriously adverb
  • nonserious adjective
  • nonseriously adverb
  • overserious adjective
  • overseriously adverb
  • quasi-serious adjective
  • quasi-seriously adverb
  • seriousness noun
  • superserious adjective
  • superseriously adverb
  • ultraserious adjective
  • ultraseriously adverb
  • unserious adjective
  • unseriously adverb

Etymology

Origin of serious

First recorded in 1400–50; late Middle English, from Middle French serieux and Latin sērius “grave, earnest” or Late Latin sēriōsus; -ous, -ose 1

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.