n. (also d) (pl. Ds or D's) 1 the fourth letter of the alphabet. 2 Mus. the second note of the diatonic scale of C major. 3 (as a Roman numeral) 500. 4 = DEE. 5 the fourth highest class or category (of academic marks etc.).
D
Meaning of D in English
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012