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
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
It was bad enough having Count Olaf acting in loco parentis and announcing himself as their father, but to consider this man her husband, even for the purposes of a play, was even more dreadful.
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
Should you eat the papas bravas the same night as the chicharrones locos, you may wish they did not both depend on the pineapple hot sauce and the cashew cream.
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
Reeking of oil and money, the town is attracting the usual motley con men and drifters, losers and locos.
From Time Magazine Archive
Cicero expresses himself plainly on this subject: “Qui multa voluerit meminisse, multa sibi loca comparet: oportet multos comparare locos, ut in multis locis multas imagines collocemus.”
From Curiosities of Medical Experience by J. G. (John Gideon) Millingen
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
Oh, yes," agreed the girl, "there's not a doubt but that she's plumb locoed!
From Hope Hathaway A Story of Western Ranch Life by Frances Parker
Yuh've made many things plain to me that I was too locoed to see before.
From The Song of the Wolf by Frank Mayer
Oh, she's a little locoed, but barrin' that she's smarter'n a steel trap.
From Hope Hathaway A Story of Western Ranch Life by Frances Parker
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
