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1.
Pumpsin pertains to a situation upon whence one is having a bangin' time, either at a social event whilst one is off one's barnet, or in a sexual situation where one maybe pumpsin the fuck out of someone.
Fuck me guys i was pumpsin at that party last night, I think I shat on someone's leg.

She was hot as fuck, I was pumpsin her til Ceefax stopped and Breakfast T.V came on.
by ElMatador3000 October 11, 2009