In the act of wiping one's bottom, when the toilet paper tears and, inadvertently, a finger plunges into the butt hole. (Occurs especially when using cheap toilet paper or when wiping too hard). Can result in a stinky fingernail.
Guy in toilet: Oh, dude, gross!
Guy outside: What happened?
Guy in toilet: I was wiping and I accidentally did the one-fingered butt plunge.
Guy outside: What happened?
Guy in toilet: I was wiping and I accidentally did the one-fingered butt plunge.
by LongWayfromHome September 7, 2010