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.
3. the bulb of the onion plant.
4. the flavor or odor of this bulb.
5. 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.

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
3. any of several related plants similar to A. cepa, such as A. fistulosum (Welsh onion)
4. know one's onions slang.
   to be fully acquainted with a subject

Derived Forms

• ˈoniony, adjective

Other Words From

• onion·like adjective
• onion·y adjective

Word History and Origins

Origin of onion¹

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

Word History and Origins

Origin of onion¹

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

Idioms and Phrases

Idioms

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

More idioms and phrases containing onion

see know one's stuff (onions) .

Example Sentences

McDonald’s also announced that recent tests showed no E. coli in its food, and its Quarter Pounder burgers topped with slivered onions are now back on menus nationwide.

From Salon

In October, more than 100 McDonald’s customers were sickened by an E. coli outbreak in the U.S. linked to slivered onions.

From Los Angeles Times

The E. coli cases linked to carrots comes after another high-profile outbreak in the US, related to slivered onions on some McDonald's Quarter Pounder burgers.

From BBC

McDonald's said in a statement that it "identified an alternate supplier" for about 900 restaurants that had "temporarily stopped serving Quarter Pounder burgers with slivered onions".

From BBC

"He was eating a packet of Walkers cheese and onion crisps and he wasn't blinking," she said.

From BBC