Top definition
The act of standing astraddle over another person who is laying on the floor while you pour a beer or other clear beverage down your ass crack, thus allowing it to cascade rustily down into the other person's open mouth.
"Don't kiss that girl! She got a Rusty Waterfall last night!"
by myretardedlittlebrother December 11, 2011
Get the mug
Get a Rusty Waterfall mug for your guy Julia.