Noun: Sexual Act of Somewhat Questionable Outcome.
Warning: illegal in most Middle Eastern countries; may lead to lowered sense of self worth or acne.
Merhod: During oral sex, hold the back of the head in place and take a hard piss, when the piss comes out of the nose it is a Reverse Waterfall.
You think backdrop is bad? Try a Reverse Waterfall
When a female ejaculates so hard her pussy fluid squirts up your chest from your waist.
Last night I fucked a girl so hard that her pussy reverse waterfalled me.