(Science: botany) 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.
(Science: zoology) Onion fish, a dipterous insect whose larva feeds upon the onion; especially, anthomyia ceparum and Ortalis flexa. Welsh onion.
Origin: F. Ognon, fr. L. Unio oneness, unity, a single large pearl, an onion. See One, Union.