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.
It is far higher than it was even during the giddy, insane days at the peak of the great dot-com bubble a quarter-century ago.
From MarketWatch ● Nov. 6, 2026
I am returning to a world carefully crafted to drive me insane, but armed with knowledge I lacked when I left.
From Slate ● Nov. 1, 2026
We are introduced to a former housemaid, who, before being diagnosed as insane, was “up before dawn with scuttle bucket and shovel, home in the dark to the thatch dripping soot.”
From The Wall Street Journal ● Oct. 30, 2026
She was probably relieved when the jeeps turned up for another day trip, and Romesh was all of us with his hilarious reaction to news of yet another insane mission.
From BBC ● Oct. 29, 2026
I was going to shriek like an insane woman who has been locked in an attic for a great many years.
From "Okay for Now" by Gary D. Schmidt
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Get a wordDefinitions 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.
