What is the meaning of Onion?

A monocotyledonous plant (Allium cepa), allied to garlic, used as vegetable and spice.

The bulb of such a plant.

A plant of the genus Allium as a whole. (Can we add an example for this sense?)

An ounce.

A ball.

A watch-seal.

Alternative letter-case form of Onion (an inhabitant of Bermuda; a Bermudian)

Alternative form of wynwyn (onions)

Source: wiktionary.org