A big idiot. Usually an affectionate term for someone who is your friend, but acts like a complete idiot.
Comes from the Soulja Boy song "Bootymeat". Just substitute "idiot" for "booty".
Soulja Boy: "Girl, shake that idiotmeat. That idiotmeat. That idiotmeat. That idiotmeat. Girl, shake that idiotmeat, all up on me."
Morgan: "Just want to let you know: I've self-diagnosed myself with HAJ. Unfortunately, there's no cure, so it's just going to be something we have to keep dealing with. Please support me in this time of personal distress."
Jessica: "HAJ? Hilarious Apple Jalapeno?"
Morgan: "No. Hyperactivity Around Jessica."
Jessica: "You are USDA-approved, Grade A idiotmeat."