O \O\ ([=o]), n.; pl. O's or Oes ([=o]z).

1. The letter O, or its sound. ``Mouthing out his hollow oes and aes.'' --Tennyson.

2. Something shaped like the letter O; a circle or oval. ``This wooden O [Globe Theater]''. --Shak.

3. A cipher; zero. [R.]

Thou art an O without a figure. --Shak.

Source: Webster's Revised Unabridged Dictionary (1913)