onion Meaning, Definition & Usage

  1. noun the bulb of an onion plant
  2. noun bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
    Allium cepa; onion plant.
  3. noun an aromatic flavorful vegetable

WordNet

On"ion noun
Etymology
F. ognon, fr. L. unio oneness, unity, a single large pearl, an onion. See One, Union.
Definitions
  1. (Bot.) A liliaceous plant of the genus Allium (A.cepa), having a strong-flavored bulb and long hollow leaves; also, its bulbous root, much used as an article of food. The name is often extended to other species of the genus.

Webster 1913