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
“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
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
And it looks like vegan chicharrones locos at El Rey.
From New York Times ● Jul. 28, 2015
Some of the locos blow up a few feet and settle back on the tracks as if heaving a big sigh.
From Time Magazine Archive
The roll was called: seven "good and true" locos answered the call.
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
"Crazy as a locoed cow," Red whispered across the room to Buck, who nodded sorrowfully and went into the cook shack.
From Hopalong Cassidy by Clarence E. Mulford
Once more, I guess, I was locoed for the minute.
From The Real Man by Francis Lynde
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
The old Sage Brush local is locoed 'way up toward S'liny.
From The Reclaimers by Margaret Hill McCarter
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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.
