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.
di Dante Rau 20 luglio 2006
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
di Roger Podacter 19 settembre 2010