When you piss on the side of the bowl of the toilet instead of the water to make less noise at night.
Mom: Johnny, if you're staying up late tonight be sure to mute your piss so you don't wake me up.

Another example:
Friend 1: Hey I have to piss. What if I wake your parents?
Friend 2: Dude just use Piss Muting.
Friend 1: Great idea why didn't I think of that?
by the way... July 8, 2013
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