insanity
Americannoun
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(not in technical use as a medical diagnosis) the condition of being insane; a derangement of the mind.
- Synonyms:
- madness, lunacy, aberration, mania, craziness
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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.
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Psychiatry. (formerly) psychosis.
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extreme foolishness.
Trying to drive through that traffic would be pure insanity.
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a foolish or senseless action, policy, statement, etc..
We've heard decades of insanities in our political discourse.
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noun
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relatively permanent disorder of the mind; state or condition of being insane
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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
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utter folly; stupidity
Other Word Forms
Etymology
Origin of insanity
First recorded in 1580–90; from Latin insānitāt-, stem of insānitās “unsoundness of mind, insanity”; see origin at in- 3, sanity
Explanation
Insanity is an ongoing state of extreme mental illness, which may cause abnormal or antisocial behaviors. If you bark at cats and meow at dogs, you might suffer from insanity. The noun insanity originates from the Latin word insanitatem, meaning "unhealthfulness" relating to the mind. It is believed that master artist Vincent van Gogh, who cut off his ear and gave it to a prostitute, experienced periods of insanity. But this term can also refer to things people perceive as unconventional or foolish, like your neighbor who quit his job, sold all his belongings, and bought a boat to sail around the world.
Vocabulary lists containing insanity
Adrift
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salu, san (health)
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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.
Despite Jane Wickline’s delightfully awkward cringe and Sarah Sherman’s delectable insanity, only one “Saturday Night Live” cast member picks up votes this round.
From Los Angeles Times • May 20, 2026
Barabak: A popular expression — which Steyer mentioned — defines insanity as doing the same thing over and over and expecting a different result.
From Los Angeles Times • May 15, 2026
“Man on Fire” does what thrillers do, accelerating into insanity toward the end of its seven episodes, becoming increasingly implausible, frenetic and rife with coincidence.
From The Wall Street Journal • Apr. 30, 2026
She was reportedly found not responsible by reason of insanity.
From BBC • Apr. 15, 2026
Now Peeta’s worried about me, which adds to the insanity of it all.
From "Catching Fire" by Suzanne Collins
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
