adjective
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slang insane
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(of an animal) affected with loco disease
noun
verb
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to poison with locoweed
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slang to make insane
noun
adjective
Other Word Forms
Noun Inflected Forms
Etymology
Origin of loco
1835–45, < Spanish: insane
Explanation
If someone calls you loco, it means they think you're nutty or eccentric. Your friends will think your dog is completely loco if she spends hours every day chasing her own tail. You can use the slang term loco when you're commenting on the craziness or irrationality of a person or situation. You might say, for example: "This meeting is totally loco — everyone's talking at the same time!" Loco comes from American English, which borrowed it from the Spanish loco, "insane." Its roots are uncertain, but it may stem from the Arabic lauqa, "fool."
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.
See Examples For:
Coaches often serve in loco parentis, guiding a developing prospect not only through training and tournaments but also the awkward riddles of growing up.
From The Wall Street Journal ● Dec. 23, 2025
"The loco pilot, on observing the herd of elephants, applied emergency brakes. However, elephants dashed with the train," he said.
From Barron's ● Dec. 20, 2025
He was also asked about his understanding of the term "in loco parentis", namely having responsibilities for children in the absence of their parents or guardians.
From BBC ● Jan. 24, 2024
She also sells tostadas topped with chow mein, elote loco and rellenitos — plantains stuffed with refried black beans.
From Los Angeles Times ● Dec. 23, 2023
“So your pelo loco, like clippings of grass, will not disarrange this house,” she says.
From "Beast Rider" by Tony Johnston & María Elena Fontanot de Rhoads
Someone who prefers potatoes is getting way less for their money than someone who’s locos for Doritos.
From The Verge ● Jan. 6, 2022
And it looks like vegan chicharrones locos at El Rey.
From New York Times ● Jul. 28, 2015
Just after I accepted the fact that I was in love with a dish called vegan chicharrones locos, a phrase from Freud ran through my head.
From New York Times ● Jul. 28, 2015
People around here, they call this place the casa de locos, but they don't understand.
From Time Magazine Archive
Be sure his wife and her allies left him no locos pœnitentice.
From For the Cause by Stanley J. Weyman
Moreover, he is locoed and has other defects.
From Time Magazine Archive
"Well, if he ain't bughouse, he is sure locoed on that wife of his."
From The Great Gold Rush A Tale of the Klondike by W. H. P. (William Henry Pope) Jarvis
Reckon I must ’a’ been locoed, or, like ’nuff that ar ole hermutt’s done played a trick on me.
From Two Wyoming Girls and Their Homestead Claim A Story for Girls by Carrie L. Marshall
He uttered his mind again concerning the work of Sydenham, the master Teevan had prescribed, asserting that unsuspecting toiler to be hopelessly "locoed" in the matter of color.
From Ewing\'s Lady by Harry Leon Wilson
Reckon he’s been used mighty rough to be locoed and crippled up the way he is.”
From The Snow-Burner by Henry Oyen
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.
