[ in-seyn ]
See synonyms for: insaneinsanelyinsaneness on

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

  2. of, relating to, or characteristic of a person who is mentally deranged: a wild and insane look on her face.

  1. 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.

  2. temporarily unable to think clearly: I think I'm going insane from all the noise outside.

  3. utterly senseless: an insane plan.

  4. Slang. excessive or extravagant; extreme: This much snow in April is just insane!

  5. Slang. astonishingly great; wonderful: Without his insane performance, the film would've been a total flop.

Origin of insane

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

synonym study For insane

5. See mad.

Other words for insane

Other words from insane

  • in·sane·ly, adverb
  • in·sane·ness, noun
  • pseu·do·in·sane, adjective

Words Nearby insane Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use insane in a sentence

British Dictionary definitions for insane


/ (ɪnˈseɪn) /

    • mentally deranged; crazy; of unsound mind

    • (as collective noun; preceded by the): the insane

  1. characteristic of a person of unsound mind: an insane stare

  1. irresponsible; very foolish; stupid

Derived forms of insane

  • insanely, adverb
  • insaneness, noun

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