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
Synonym Usage
See mad.
Other Word Forms
Etymology
Origin of insane
First recorded in 1550–60; from Latin insānus “unsound (of mind), demented, frenzied”; see origin at in- 3, sane
Explanation
To be insane is to have a seriously disordered state of mind. This is also a slang word for acting wacky or wild. This word has two closely related meanings. People who are insane are suffering from a seriously irrational or disordered state of mind. When someone commits a crime, it's important to know if they were sane or insane. If they're insane, the penalty is different. Many uses of the word are not so serious. A wild party is called insane, and car salesmen say their prices are insane. A teacher assigning six hours of homework might be told "That’s insane!"
Vocabulary lists containing insane
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.
“I remember feeling an insane amount of adrenaline and anxiety,” Fuld said.
From The Wall Street Journal ● Aug. 24, 2026
Festivalgoers who saw EsDeeKid's set in east London described it as "absolutely insane" with "constant energy".
From BBC ● Aug. 24, 2026
With Amanda and I doing ‘Whateverrr!’ you didn’t see a Black girl and a white girl, you just saw these two insane girls who loved the same guys.
From Los Angeles Times ● Aug. 15, 2026
"It is one of the most insane days in Norwegian history."
From BBC ● Jul. 6, 2026
This is all completely insane, and every new piece of information only compounds the insanity.
From "Girl in the Blue Coat" by Monica Hesse
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.
