often capitalized, often attributive
1
a : the 21st letter of the English alphabet
b : a graphic representation of this letter
c : a speech counterpart of orthographic u
2
: a graphic device for reproducing the letter u
3
: one designated u especially as the 21st in order or class
4
[abbreviation for unsatisfactory]
a : a grade rating a student's work as unsatisfactory
b : one graded or rated with a U
5
: something shaped like the letter U