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onion

[ uhn-yuhn ]
/ ˈʌn yən /
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noun
adjective
containing or cooked with onions: onion soup.
of, relating to, or resembling an onion.
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Idioms about onion

    know one's onions, Slang. to know one's subject or business thoroughly; be capable or proficient.

Origin of onion

1325–75; Middle English onyon<Old French oignon<Latin ūniōn- (stem of ūniō) a unity, large pearl, onion; see union

OTHER WORDS FROM onion

on·ion·like, adjectiveon·ion·y, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

How to use onion in a sentence

British Dictionary definitions for onion

onion
/ (ˈʌnjən) /

noun
an alliaceous plant, Allium cepa, having greenish-white flowers: cultivated for its rounded edible bulb
the bulb of this plant, consisting of concentric layers of white succulent leaf bases with a pungent odour and taste
any of several related plants similar to A. cepa, such as A. fistulosum (Welsh onion)
know one's onions British slang to be fully acquainted with a subject

Derived forms of onion

oniony, adjective

Word Origin for onion

C14: via Anglo-Norman from Old French oignon, from Latin unio onion, related to union
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with onion

onion

see know one's stuff (onions).

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
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