/yooh/ , n. , pl. U's or Us, u's or us .
1. the 21st letter of the English alphabet, a vowel.
2. any spoken sound represented by the letter U or u, as in music, rule, curious, put, or jug.
3. something having the shape of a U.
4. a written or printed representation of the letter U or u.
5. a device, as a printer's type, for reproducing the letter U or u.