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:
This is a place that has driven the Three Lions absolutely loco.
From The Wall Street Journal ● Jul. 5, 2026
"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
Starting with an ominous echoing sound, he begins to sing “Como Basquiat, ‘toy bien loco como Basquiat” over a simple trap beat.
From Los Angeles Times ● Oct. 1, 2024
On the return journey, a bolt sheared on what is now more widely known as the Penydarren loco, causing the boiler to leak.
From BBC ● Feb. 24, 2024
“She’s a judge, and she’d just start babbling about in loco parentis like Mr. Poe.”
From "The Bad Beginning" by Lemony Snicket
Someone who prefers potatoes is getting way less for their money than someone who’s locos for Doritos.
From The Verge ● Jan. 6, 2022
Recommended Dishes Vegan chicharrones locos; papas bravas; shaved cauliflower; green mole with burrata; sardine tostada; octopus salad.
From New York Times ● Jul. 28, 2015
And it looks like vegan chicharrones locos at El Rey.
From New York Times ● Jul. 28, 2015
Thanks to the cold Humboldt Current, Chile has the world's most unusual seafood: erizos, giant sea urchins; picoroccos, beaked shell fish that taste like crab; and the giant abalones known as locos.
From Time Magazine Archive
"Beat, by thunder!" roared the locos, in grand chorus; and in the modern classics of the Bowery, "they wasn't any thing else."
From The Humors of Falconbridge A Collection of Humorous and Every Day Scenes by Falconbridge
Moreover, he is locoed and has other defects.
From Time Magazine Archive
"The old man is a bit locoed on this rebellion theory," mused Herbert as he went along.
From The Great Gold Rush A Tale of the Klondike by Jarvis, W. H. P. (William Henry Pope)
"Of all th' locoed layouts I ever run up against this here mesa top takes th' prize," he finished in disgust.
From Hopalong Cassidy by Mulford, Clarence E.
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 Marshall, Carrie L.
He’s a pretty bird, but if he’s locoed, he’d better be dead than afoot—poor creature.”
From Ruth Fielding In the Saddle College Girls in the Land of Gold by Emerson, Alice B.
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.
