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.
containing or cooked with onions: onion soup.
of, relating to, or resembling an onion.
Idioms about onion
know one's onions, Slang. to know one's subject or business thoroughly; be capable or proficient.
- on·ion·like, adjective
- on·ion·y, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
British Dictionary definitions for onion
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
- 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
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.