Rocky Waterfall 

To have a 'Rocky Waterfall' is to simultaneously urinate while having a dump.

Example 1. "I was so desperate for a wee, that when I was shitting I pissed at the same time. It looked like a rocky waterfall."

Example 2. "I was desperate for some really kinky porn, so I looked up golden showers with scat. What I got can only be described as a rocky waterfall"

Rocky Waterfall by Lord Dangleballs August 13, 2016

rock waterfall 

Urinating on one's own scrotum, often by accident.

Steve's pants were too tight, and it was very hot out. He had to keep drinking water, so inevitably he wound up having to pee. He entered a McDonald's, and when he got into the bathroom, he realized he also needed to poop. So he sat down on the toilet, and as he let out his stream of urine, he did not yet realize the degree to which sweat had glued his scrotum to his shaft, and received a rock waterfall.

rock waterfall by Eric Jean April 18, 2018