I. C 1 BrE AmE , c /siː/ noun ( plural C’s , c’s ) [uncountable and countable]
1 . the third letter of the English alphabet
2 . the first note in the musical ↑ scale of C ↑ major , or the musical ↑ key based on this note
3 . a mark given to a student’s work to show that it is of average quality
4 . the number 100 in the system of ↑ roman numeral s
II. C 2 BrE AmE
1 . the written abbreviation of Celsius or Centigrade :
Water boils at 100°C.
2 . written informal a way of writing ‘see’, used especially in emails and ↑ text message s :
CU (=see you) in class!