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
It’s been bien loco, like I say in the song.
From Los Angeles Times ● Sep. 4, 2025
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
“Are you familiar with the Latin term ‘in loco parentis’?” he asked.
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
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
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
Those locos were worth to us more than a king's ransom!
From With the Guards' Brigade from Bloemfontein to Koomati Poort and Back by Edward P. Lowry
Moreover, he is locoed and has other defects.
From Time Magazine Archive
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
If the family cow becomes locoed or shows an unusual result in her milk product, should one consult a piano tuner?
From Farm Boys and Girls by William Arch McKeever
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
If locoed animals can be turned into a field of alfalfa, a large proportion of them will recover with no further treatment.
From Special Report on Diseases of Cattle by United States. Bureau of Animal Industry
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.
