Onion (?), n. [F. ognon, fr. L. unio oneness, unity, a single large pearl, an onion. See One, Union.]
1. (Bot.) A liliaceous plant of the genus Allium (Allium 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.
[1913 Webster]
2. The flavor of an onion1.
[PJC]
Onion fish (Zool.), the grenadier. -- Onion fly (Zool.) a dipterous insect whose larva feeds upon the onion; especially, Anthomyia ceparum and Ortalis flexa. -- Welsh onion. (Bot.) See Cibol. -- Wild onion (Bot.), a name given to several species of the genus Allium.
[1913 Webster]