abbreviation 1. [Physics] barn(s). 2. (b.) -- born (used to indicate a date of birth) * George Lloyd (b. 1913). 3. billion. 4. bass. 5. basso. B1 /be / b I. noun 1. the second letter of the alphabet. 2. the second highest class of academic mark. 3. denoting the second-highest-earning socioeconomic category for marketing purposes, including intermediate management and professional personnel. 4. (b) -- [Chess] denoting the second file from the left, as viewed from White's side of the board. 5. (usu. b) -- the second constant to appear in an algebraic equation. 6. [Geology] denoting a soil horizon of intermediate depth, typically the subsoil. 7. the human blood type (in the ABO system) containing the B antigen and lacking the A. 8. (usu. B) -- [Music] the seventh note of the diatonic scale of C major. 9. a key based on a scale with B as its keynote. II. phrases plan