the process in which the vagina in stimulation produces its own lubricant(or marinade) and begins a pull on the shaft of the penis...

some say scientifically this is a reaction to pull semen closer to the uterus......

also the constriction of the vaginal walls mimicing a swallowing sensation
Nic watched as i nailed that chick so hard she got all bothered and caused an upsuck so hard on my schlong.....it pulled all the skin up to the head of my dick to where i didnt have enough skin left to close my eyes.

The upsuck of that chicks ass was like someone drinking out of a garden hose in the summer.
by jere from smackjab April 19, 2008
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