onion Definition

onion
noun

1. Any of numerous varieties of a biennial plant belonging to the lily family, native to SW Asia.
2. The edible bulb of this plant, which consists of white fleshy scales and a pungent oil, surrounded by a brown papery outer layer, and is eaten raw, cooked or pickled.
3. The long tubular leaves of a young onion plant (called a spring onion), eaten as a salad vegetable.

Derivative: onion-like
adj

Derivative: oniony
adj

Idiom: know one's onions

colloq
To know one's subject or job well.

Etymology: 14c: from Anglo-Norman union, from French oignon, from Latin unio unity, a large pearl, or an onion.