noun, plural locos.
Slang. an insane person; maniac.
Veterinary Pathology, locoism.
verb (used with object), locoed, locoing.
to poison with locoweed.
Slang. to cause to be insane or crazy.
Slang. out of one's mind; insane; crazy.

1835–45, Americanism; < Spanish: insane

Dictionary.com Unabridged

in loco

[in loh-koh]
in place; in the proper place.


in loco parentis

[in loh-koh pah-ren-tees; English in loh-koh puh-ren-tis]
in the place or role of a parent.

loco citato

[loh-koh ki-tah-toh; English loh-koh sahy-tey-toh, si-tah-toh]

loco primo citato

[loh-koh pree-moh ki-tah-toh; English loh-koh prahy-moh sahy-tey-toh, pree-moh si-tah-toh] .

loco supra citato

[loh-koh soo-prah ki-tah-toh; English loh-koh soo-pruh sahy-tey-toh, si-tah-toh]

suo loco

[soo-oh law-koh; English soo-oh loh-koh]
in one's own or rightful place.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
in loco parentis (ɪn ˈləʊkəʊ pəˈrɛntɪs)
in place of a parent: said of a person acting in a parental capacity

loco1 (ˈləʊkəʊ)
informal short for locomotive

loco2 (ˈləʊkəʊ)
1.  slang chiefly (US) insane
2.  (of an animal) affected with loco disease
n , -cos
3.  short for locoweed
4.  to poison with locoweed
5.  slang (US) to make insane
[C19: via Mexican Spanish from Spanish: crazy]

loco3 (ˈləʊkəʊ)
denoting a price for goods, esp goods to be exported, that are in a place specified or known, the buyer being responsible for all transport charges from that place: loco Bristol; a loco price
[C20: from Latin locō from a place]

loco citato (ˈlɒkəʊ sɪˈtɑːtəʊ)
loc. cit, Abbreviation: lc in the place or passage quoted
[Latin: in the place cited]

suo loco (ˈsuːəʊ ˈlɒkəʊ)
chiefly law in a person or thing's own or rightful place

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

in loco parentis
1710, from L., lit. "in the place of a parent."

1844, Amer.Eng., from Sp. loco (adj.) "insane," of uncertain origin, perhaps from Arabic lauqa, fem. of 'alwaq "fool, crazy person." Loco-weed (1879) was name given to species of western U.S. plants that cause cattle and horse diseases that make them stagger and act strangely.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Cultural Dictionary
in loco parentis [(in loh-koh puh-ren-tis)]

To assume the duties and responsibilities of a parent: “Because Jack's parents were out of town, his sister acted in loco parentis and punished him for staying out so late.” From Latin, meaning “in the place of a parent.”

Note: At one time, colleges and universities acted in loco parentis for their students, but this is no longer true.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
And, a concerned parent who thinks the kids have gone loco has scuttled many a sale.
Object, such as a trailer, fouling right-of-way of loco-motive.
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