To
slap a stream of urine back and forth with one's
flat-palmed hand. Can be a solo or group activity performed by either
gender. Generally practised at urinals and public toilets.
"I'll be
right back, gotta go take a pisswhack"
"My game was on point that
night, I pisswhacked at a rate of 329wpm (whacks per minute)"
"I pisswhacked the shit outta this guy's stream at the urinal last
night, his expression was one of liberation"
"Some guy started pisswhacking me at the urinal, the experience has brought me closer to Jesus"