imbb Share definition Flag 1. An acronym meaning "it might be bad."2. An acronym meaning "I might be black." Person 1: I want to date your ex. Are you ok with that. Person 2: Don't do it: imbb.Person: I have a large penis. Imbb. imbb by lsmnr November 18, 2010 0 0 Get merch Get the imbb mug. Buy Now — $32.95 See more merch