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.
Howard said he posted about his ER bill because “I feel like most people probably relate as far as hospitals trying to upcharge an insane amount,” he said.
From The Wall Street Journal ● Oct. 7, 2026
"It is actually insane but I am so proud of him," she told the BBC.
From BBC ● Sep. 28, 2026
She slammed property prices across the country as "completely insane".
From Barron's ● Sep. 28, 2026
Yann LeCun, former chief AI scientist at Meta, posted that this analysis was “a welcome dose of sanity in an otherwise insane debate.”
From The Wall Street Journal ● Sep. 16, 2026
He went temporarily insane and we took him to a doctor and he got a pill and now he’s better and wants to see you?
From "Breadcrumbs" by Anne Ursu
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.
