insane
Americanadjective
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(not in technical use as a medical diagnosis) not sane; not of sound mind; mentally deranged.
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of, relating to, or characteristic of a person who is mentally deranged.
a wild and insane look on her face.
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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.
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temporarily unable to think clearly.
I think I'm going insane from all the noise outside.
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utterly senseless.
an insane plan.
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Slang. excessive or extravagant; extreme.
This much snow in April is just insane!
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Slang. astonishingly great; wonderful.
Without his insane performance, the film would've been a total flop.
adjective
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mentally deranged; crazy; of unsound mind
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( as collective noun; preceded by the )
the insane
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characteristic of a person of unsound mind
an insane stare
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irresponsible; very foolish; stupid
Related Words
See mad.
Other Word Forms
- insanely adverb
- insaneness noun
- pseudoinsane adjective
Etymology
Origin of insane
First recorded in 1550–60; from Latin insānus “unsound (of mind), demented, frenzied”; in- 3, sane
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.
But they were also about to prove that they were already better than most humans at making sense of a tournament known for being completely insane.
From The Wall Street Journal • Mar. 24, 2026
Another added: "It would be insane to challenge the patient."
From BBC • Mar. 11, 2026
When the Islamic revolution happened in 1979, they said, This is an insane system, a monarchy, that the son of the current guy is the person who’s going to rule until he dies.
From Slate • Mar. 11, 2026
But the effervescent co-host of the hit “Girls Gotta Eat” podcast will do more than just tell her “crazy, insane stories for an hour.”
From Los Angeles Times • Feb. 27, 2026
Here’s how you practice shrieking like an insane woman who has been locked in an attic for a great many years: You stand in the middle of the field.
From "Okay for Now" by Gary D. Schmidt
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.
