In the act of masturbating to online pornography, when your hand reaches the top of your shaft and slams the desk and creates a thunder-like sound.
person 1: Is it storming outside? I hear thunder but I don't see any lightning.
person 2: Oh that's just John in the next room over thunder fapping. He must be watching some good stuff.
person 2: Oh that's just John in the next room over thunder fapping. He must be watching some good stuff.
by Spilner April 15, 2011
by pimpassnigga September 11, 2012