Mouthterbating 

Slang for autofellatio, or when you masturbate with your own mouth.

Last night I was mouthterbating. My mouth still tastes salty!

Mouthterbating by Mouthterbating August 30, 2014

mathterbating 

Doing math for fun, enjoyment, entertainment and/or to pleasure ones self.

Dude1: Hey! whats that nerd over there doing with that calculator?
Dude2: Probably mathterbating
Dude1: Dude! sick he could at least go to the bathroom to do dat
Dude2: Gotta do what you gotta do

mathterbating by SeakingFuckYeah! March 4, 2008