pee hammer
While a male is taking a piss, the penis is clamped down upon preventing further discharge resulting in an internal backup of fluids (aka a water hammer) that causes extreme pain.
I was taking a shower with my girlfriend and had to pee, so I pissed on her feet and she turned around and grabbed my junk causing a pee hammer.
pee hammer by UnCivil Engineer December 23, 2011
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