"Just like my Dick", a phrase said after someone makes a sexual innuendo about a dick without knowing it. Sometimes it makes sense and other times not. Its a fun game for two people to play around others while around others who do not know what JLMD means.
Person one: "Wow! This home work is hard!"
Person two: "JLMD man..."
Person one: "Dude this is huge!"
Person two: "JLMD!"
Person one: "Hey, its Giant_white_guy."
Person two: "Heh, JLMD."