Derived from the mullet-descriptor 'business in the front, party in the back', the stage where a man's hair is too long in the back to be considered acceptable or uniform with the rest of the hair, and too short to be considered a mullet.
Person 1: " Dude, what's going on with your hair? Two more weeks without a trim and you'll be a full on Joe Dirt."
Person 2: "Yeah, I know; I need to get rid of this happy-hour ASAP! And, its pronounced 'Dirte.'"