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3.
Jacking off while fingering your butthole, with the result being intense sexual pleasure.
After Pat's underwear were frozen, he sat in his room and gave himself a jumpkin.
by jackinit April 03, 2005
 
1.
Much like a blumpkin where you get blowy while dropping off a SEAL team, its when you jack off and take a shit at the same time because you're stuck in some third world shithole or... your parents house.
dude 1 walks into the bathroom
dude 1: hey man, hows it going? you've been in here a minute.

dude 2: it was going good until you interrupted my jumpkin
by 9223-beotch April 03, 2013
 
2.
The act of making yourself cum while simultaneously dropping a deuce.
My girlfriend wouldnt give me a blumpkin because apparently she hates the smell of my deuce, so I went into the bathroom and gave myself a jumpkin.
by usmc_nightmare March 25, 2010