Abbreviation for Mart Dawg. Title given to someone an overly attractive person who is one of a kind in who they are and what they do. Specifically, M.D.s have a doctorate in slaying pussy and eating ass. They are also great friends and will give you sexual favors when you are feeling down.
Friend 1: Yo Mart Dawg, I just got a call back from the hiring manager, I didn't end up getting the job.
Friend 2 ( M.D. ): Sorry to hear that bro, everything okay? Come over here and let me give you a brojob.