• synonyms


See more synonyms for insanity on Thesaurus.com
noun, plural in·san·i·ties.
  1. the condition of being insane; a derangement of the mind.
  2. Law. such unsoundness of mind as frees one from legal responsibility, as for committing a crime, or as signals one's lack of legal capacity, as for entering into a contractual agreement.
  3. Psychiatry. (formerly) psychosis.
    1. extreme foolishness; folly; senselessness; foolhardiness: Trying to drive through that traffic would be pure insanity.
    2. a foolish or senseless action, policy, statement, etc.: We've heard decades of insanities in our political discourse.
Show More

Origin of insanity

From the Latin word insānitās, dating back to 1580–90. See in-3, sanity
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for insanity

madness, craziness, absurdity, folly, frenzy, alienation, dementia, lunacy, hysteria, irresponsibility, psychopathy, phobia, aberration, delusion, dotage, senselessness, neurosis, unbalance, mania, derangement

Examples from the Web for insanity

Contemporary Examples of insanity

Historical Examples of insanity

British Dictionary definitions for insanity


noun plural -ties
  1. relatively permanent disorder of the mind; state or condition of being insane
  2. law a defect of reason as a result of mental illness, such that a defendant does not know what he or she is doing or that it is wrong
  3. utter folly; stupidity
Show More
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 insanity


1580s, "state of being insane," from Latin insanitatem (nominative insanitas) "unhealthfulness," noun of quality from insanus (see insane). Meaning "extreme folly" is from 1844.

Show More
Online Etymology Dictionary, © 2010 Douglas Harper

insanity in Medicine


  1. Persistent mental disorder or derangement. Not in scientific use.
  2. Unsoundness of mind sufficient in the judgment of a civil court to render a person unfit to maintain a contractual or other legal relationship or to warrant commitment to a mental health facility.
  3. In most criminal jurisdictions, a degree of mental malfunctioning considered to be sufficient to relieve the accused of legal responsibility for the act committed.
Show More
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.