The act of sitting on the top part of a toilet and shitting while getting head by the girl who is strattling towards you on the bottom seat while also taking a dump at the same time.
The raunchiest act of the famous "blumpkin" to the next extreme calling it the Upper Decker Double Blumpkin.
When a man is taking a dump in the tank of a toilet while a female is sitting on the bowl taking a dump while facing him and performing oral sex on him.
Yo I was taking a shit and Tracy want to give me a blumpkin but she also had to take a shit so we did an Upper Decker Double Blumpkin
An event when two couples receive phalacio while defecating in the bowl and in the tank.
"Yo Dawg, did you hear Shaniqua was in a Upper Decker Double Blumpkin' last night?'