The act of practicing for a blumpkin by jerking yourself off while taking a dump.
I tried to give myself a jerumpkin as practice before my girl gave me a blumpkin.
A poop stain on the back of the terlet(toilet)seat that is left after sitting too far back while performing a jerumpkin.
After finishing a very satisfying jerumpkin, I got up turned around and noticed jerumpkin shrapnel on the terlet seat.