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. slang,  to be fully acquainted with a subject

Other Word Forms

• onionlike adjective
• oniony 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, to know one's subject or business thoroughly; be capable or proficient.

see know one's stuff (onions).

Example Sentences

Slatkin’s next project is a candle made for White Castle, with tones of pickles, onions and ketchup designed to smell like the burger chain’s popular slider.

Read more on Wall Street Journal

Straight from my grandmother’s recipe card: melted butter, grainy Dijon, a dollop of mayo, a splash of Worcestershire, garlic and onion powders, a little brown sugar, and a shower of poppy seeds.

Read more on Salon

The rice field is surrounded by potato, onion and beet crops, which are still the thriving staples here.

Read more on BBC

“We are continuing to work with our green onion supplier to determine the root cause.”

Read more on Salon

You’ll find “vegetable casserole,” a swamp of canned onions, frozen peas and carrots, cream of celery soup and a splash of milk.

Read more on Salon