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The fart or series of farts that occur immediately before defecation (or taking a dump). These farts smell much worse than regular farts because your poop is at it's closest point to the outside of your body.
Dude1: Dude, what is that horrible smell?

Dude2: Sorry dude, it was a predumptial fart.

Dude1: I think you need to go sit on the toilet!
by Buddahrid January 22, 2009