not sane; not of sound mind; mentally deranged.
of, relating to, or characteristic of a person who is mentally deranged: insane actions; an insane asylum.
utterly senseless: an insane plan.

Origin of insane

From the Latin word insānus, dating back to 1550–60. See in-3, sane
Related formsin·sane·ly, adverbin·sane·ness, nounpseu·do·in·sane, adjective

Synonyms for insane Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for insanest

Historical Examples of insanest

  • But if this confessed the truth, she was the insanest of women.

  • Behold now the consequence of the wilful Welshwoman's insanest of legacies!

  • No cloak of insanest belief, of dullest mistake, would henceforth hide any more the dreary nakedness of the skeleton, life!

    There and Back

    George MacDonald

  • Thus he was perfectly rational, though when others beheld him he appeared the insanest of mortals.

  • Nothing but the insanest bigotry in favor of their own conjectures could lead them to quarrel with us for expounding ours.

    Comic Bible Sketches

    George W. Foote

British Dictionary definitions for insanest



  1. mentally deranged; crazy; of unsound mind
  2. (as collective noun; preceded by the)the insane
characteristic of a person of unsound mindan insane stare
irresponsible; very foolish; stupid
Derived Formsinsanely, adverbinsaneness, 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

Word Origin and History for insanest



1550s, from Latin insanus "mad, insane; outrageous, excessive, extravagant," from in- "not" (see in- (1)) + sanus "well, healthy, sane" (see sane). Originally only of persons; of actions, from 1842. Cf. lunatic; and Italian pazzo "insane," originally a euphemism, from Latin patiens "suffering." German verrückt, literally past participle of verrücken "to displace," "applied to the brain as to a clock that is 'out of order' " [Buck]. The noun meaning "insane person" is attested from 1786.

Online Etymology Dictionary, © 2010 Douglas Harper

insanest in Medicine




Of, exhibiting, or afflicted with insanity.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.