M.B. Share definition Flag The rap name for this fucking tight ass rapper from M Mafia a.k.a. Martin Mafia. Trigger friendly, Haters envy, Roll in a Bentley, This your boy M.B., M.B. by Martin B. June 11, 2006 0 0 Get merch Get the M.B. mug. Buy Now — $32.95 See more merch