/oh/ , n. , pl. O's or Os; o's or os or oes .
1. the fifteenth letter of the English alphabet, a vowel.
2. any spoken sound represented by the letter O or o, as in box, note, short, or love .
3. something having the shape of an O.
4. a written or printed representation of the letter O or o.
5. a device, as a printer's type, for reproducing the letter O or o.