droopy, saggy, flabby ass that looks like it might spill out all over the floor once the dam holding it up is removed (i.e., pants)
I thought that girl over there in the bikini was hot, but when she turned around, her waterfall ass was so bad, I thought I was looking at Niagara falls!
by assrammers August 20, 2008
Get the waterfall assmug.