onion

[ uhn-yuhn ]

/ ˈʌn yən /

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noun

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

any of certain similar plants.

the bulb of the onion plant.

the flavor or odor of this bulb.

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

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. 2022

How to use onion in a sentence

Added to drinking water at concentrations of around one part per million, fluoride ions stick to dental plaque.
Anti-Fluoriders Are The OG Anti-Vaxxers|Michael Schulson|July 27, 2016|DAILY BEAST
In his view, a writer has only one duty: to be present in his books.
Houellebecq’s Incendiary Novel Imagines France With a Muslim President|Pierre Assouline|January 9, 2015|DAILY BEAST
Yet this, in the end, is a book from which one emerges sad, gloomy, disenchanted, at least if we agree to take it seriously.
Houellebecq’s Incendiary Novel Imagines France With a Muslim President|Pierre Assouline|January 9, 2015|DAILY BEAST
The fear of violence should not determine what one does or does not say.
Trolls and Martyrdom: Je Ne Suis Pas Charlie|Arthur Chu|January 9, 2015|DAILY BEAST

The al Qaeda-linked gunmen shot back, but only managed to injure one officer before they were taken out.
France Kills Charlie Hebdo Murderers|Nico Hines|January 9, 2015|DAILY BEAST
Practise gliding in the form of inflection, or slide, from one extreme of pitch to another.
Expressive Voice Culture|Jessie Eldridge Southwick
He alludes to it as one of their evil customs and used by them to produce insensibility.
Tobacco; Its History, Varieties, Culture, Manufacture and Commerce|E. R. Billings.
There was a rumor that Alessandro and his father had both died; but no one knew anything certainly.
Ramona|Helen Hunt Jackson
Truth is a torch, but one of enormous size; so that we slink past it in rather a blinking fashion for fear it should burn us.
Pearls of Thought|Maturin M. Ballou
Under the one-sixth they appear as slender, highly refractive fibers with double contour and, often, curled or split ends.
A Manual of Clinical Diagnosis|James Campbell Todd

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).