Know one’s onions

What is Know one’s onions?

Know one’s onions definition and meaning on Dictionary terms:
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.

 

reference: https://www.dictionary.com/browse/know-one-s-onions

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