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2.
Sloppy shit! The kind that runs down your trouser leg if you lose control. Usually after dodgy seafood, or meat with a slight 'oh that tasted weird'!
That lobster bisque must have been off. I've got the muddy waterfalls...
by Klaus October 19, 2004
 
1.
1. another word for diarrhea
2. used to describe a condition in which after anal sex, a mixture of semen and feces drip out of the anus.
1. Because I ate at taco bell, I had a muddy waterfall last night.
2. The bed sheets got wet from the muddy waterfall.
by Miguel Angel November 08, 2005
 
3.
When one urinates through the legs of another person who is defecating.
Pisser: "Bro, I really gotta piss!"

Pooper: "Dude... I'm taking a shit"

Pisser: "Whatever bro, lets muddy waterfall!"
by fuzzedhead April 30, 2011