adjective in·sane \ (ˌ)in-ˈsān \
Updated on: 22 Jan 2018

Definition of insane

1 a (1) : exhibiting a severely disordered state of mind : affected with mental illness
(2) law : affected with insanity (see insanity 2)
  • criminally insane
b : unable to think in a clear or sensible way : crazy
  • insane with jealousy
not used technically
2 : used by, typical of, or intended for mentally ill people
  • an insane asylum
3 : absurd
  • an insane scheme for making money
4 : extreme 1




play \(ˌ)in-ˈsān-nəs\ noun

Examples of insane in a Sentence

  1. The murderer was found to be criminally insane.

  2. She was insane with jealousy.

  3. He had an insane look in his eyes.

  4. She likes to drive at insane speeds.

  5. He had this insane idea that he could get rich by selling old computers.

Recent Examples of insane from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'insane.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of insane

Latin insanus, from in- + sanus sane

insane Synonyms

balmy, barmy [chiefly British], bats, batty, bedlam, bonkers, brainsick, bughouse [slang], certifiable, crackbrained, cracked, crackers, crackpot, cranky [dialect], crazed, crazy, cuckoo, daffy, daft, demented, deranged, fruity [slang], gaga, haywire, kooky (also kookie), loco [slang], loony (also looney), loony tunes (or looney tunes), lunatic, mad, maniacal (also maniac), mental, meshuga (or meshugge also meshugah or meshuggah), moonstruck, non compos mentis, nuts, nutty, psycho, psychotic, scatty [chiefly British], screwy, unbalanced, unhinged, unsound, wacko (also whacko), wacky (also whacky), wud [chiefly Scottish], around the bend, off one's gourd, off one's head, off one's rocker, out of one's head (or mind), out to lunch [slang]
balanced, compos mentis, sane, sound, uncrazy
Related Words
dotty, fey, loopy, off, potty [chiefly British], teched (or tetched), touched; aberrant, delirious, delusional, delusionary, disordered, disturbed, neurotic, obsessive-compulsive, paranoiac (also paranoic), paranoid (also paranoidal), schizoid, schizophrenic, sociopathic; eccentric, odd, oddball, pixilated (also pixillated), queer, strange; foolish, senseless, witless; irrational, unreasonable; amok (or amuck), ape, ballistic, bananas, berserk, nuclear; depressed; distracted, distraught, frantic, frenzied, haywire, hysterical (also hysteric), raving, wigged-out; fixated, monomaniac, monomaniacal, obsessed
Near Antonyms
clear, lucid, rational, reasonable; judicious, sensible, wise; healthy, normal, well-adjusted; unneurotic

INSANE Defined for Kids


adjective in·sane \ in-ˈsān \

Definition of insane for Students

1 : not normal or healthy in mind
2 : used by or for people who are insane
  • an insane asylum
3 : very foolish or unreasonable



Medical Dictionary


adjective in·sane \ (ˈ)in-ˈsān \

medical Definition of insane

1 : exhibiting a severely disordered state of mind
2 : used by, typical of, or intended for insane persons
  • an insane asylum



Law Dictionary


adjective in·sane

legal Definition of insane

: affected with insanity

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the quality or fact of being simultaneous

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