onion

[ uhn-yuhn ]

noun
  1. a plant, Allium cepa, of the amaryllis family, having an edible, succulent, pungent bulb.

  2. any of certain similar plants.

  1. the bulb of the onion plant.

  2. the flavor or odor of this bulb.

  3. Slang. a person: He's a tough onion.

adjective
  1. containing or cooked with onions: onion soup.

  2. of, relating to, or resembling an onion.

Idioms about onion

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

Origin of onion

1
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, adjective
  • on·ion·y, adjective

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

British Dictionary definitions for onion

onion

/ (ˈʌnjən) /


noun
  1. an alliaceous plant, Allium cepa, having greenish-white flowers: cultivated for its rounded edible bulb

  2. the bulb of this plant, consisting of concentric layers of white succulent leaf bases with a pungent odour and taste

  1. any of several related plants similar to A. cepa, such as A. fistulosum (Welsh onion)

  2. know one's onions British slang to be fully acquainted with a subject

Origin of onion

1
C14: via Anglo-Norman from Old French oignon, from Latin unio onion, related to union

Derived forms of onion

  • oniony, adjective

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.