From Longman Dictionary of Contemporary EnglishBB, b /biː/ noun (plural B’s, b’s) 1 SLA[countable, uncountable] the second letter of the English alphabet2 [countable, uncountable] the seventh note in the musical scale of C major or the musical key based on this note3 [countable] a mark given to a student’s work to show that it is good but not excellent I got a B in history.4 [uncountable] used to refer in a short way to one of two different things or people. You can call the first one A the advantages and disadvantages of choosing product A or B → plan B at plan1(6)5 → B4509/B1049 etc6 [uncountable] a common type of blood → from A to B at A1(6), → B-movie, B-side, B-road
Examples from the Corpus
B• She earned mostly B's this semester.b.b. (also b British English)AGEthe written abbreviation of born Andrew Lanham, b. 1885 