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insane

American  
[in-seyn] / ɪnˈseɪn /

adjective

  1. (not in technical use as a medical diagnosis) not sane; not of sound mind; mentally deranged.

    Synonyms:
    irrational, foolish, maniacal, crazy, crazed, lunatic, demented
  2. of, relating to, or characteristic of a person who is mentally deranged.

    a wild and insane look on her face.

  3. Law. considered to be or to have been affected with insanity, and therefore lacking legal responsibility or legal capacity.

    The judge deemed him criminally insane on the basis of his delusions and hallucinations.

  4. temporarily unable to think clearly.

    I think I'm going insane from all the noise outside.

  5. utterly senseless.

    an insane plan.

  6. Slang. excessive or extravagant; extreme.

    This much snow in April is just insane!

  7. Slang. astonishingly great; wonderful.

    Without his insane performance, the film would've been a total flop.


insane British  
/ ɪnˈseɪn /

adjective

    1. mentally deranged; crazy; of unsound mind

    2. ( as collective noun; preceded by the )

      the insane

  1. characteristic of a person of unsound mind

    an insane stare

  2. irresponsible; very foolish; stupid

"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 mad.

Other Word Forms

  • insanely adverb
  • insaneness noun
  • pseudoinsane adjective

Etymology

Origin of insane

First recorded in 1550–60; from Latin insānus “unsound (of mind), demented, frenzied”; in- 3, sane

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.

Predicting that Musk would make more than any person in human history, in just one year, seemed, well, insane early in 2025.

From Barron's

"That's just such an insane way to finish a tournament," said the South African after he won on extra holes for the second straight week.

From Barron's

“That was just insane to me,” she said.

From MarketWatch

“That was just insane to me,” she said.

From MarketWatch

Yet the nostalgic, and adventurous, part of me misses those insane parties.

From The Wall Street Journal