refering to or having a large, or king size, amount of the fast food in your large intestine, making it's way out through the anus. Giving one relief that they did indeed have it their way.

A large woman or man that eat a lot of Burger King and that is their fast food of choice. A connoisseur if you will of Burger King.
Dammmmmmmmm that bitch got one big Buger King Butt..

SHIT my Burger King Butt is acting up again!

Oh no, I got no control over my Burger King Butt!

That guys works hard on his Burger King Butt, he eats it everyday for lunch!
by Sara "Dirty" Vegas September 14, 2007
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