B

n. (also b) (pl. Bs or B's) 1 the second letter of the alphabet. 2 Mus. the seventh note of the diatonic scale of C major. 3 the second hypothetical person or example. 4 the second highest class or category (of roads, academic marks, etc.). 5 Algebra (usu. b) the second known quantity. 6 a human blood type of the ABO system. B film a supporting film in a cinema programme.