bathsturbater 

A person who faps in the toilet. Most often used to describe a person who habitually masturbates in public restrooms, i.e. a chronic bathsturbater.

Guy 1: "Man, Billy goes to the bathroom in the middle of this lecture every day!"
Guy 2: "Yeah man, didn't you know? Ole Bill is a bathsturbater, and he thinks the prof is sexy."
Girl 1: "Gross!"

bathsturbater by bswof22 June 24, 2012

Bathturbate 

Bathturbate
The art of bathturbating. Having a wank in the bathtub.

“Dan seems like he has a really tough time getting laid. I bet he goes home every night, runs a bubble bath and bathturbates.”

Bathturbate by Laurben February 14, 2019

Bathsturbate 

When a person masterbates while they are using the bathroom

"Kelly is such a bathsturbater! I mean she masturbating in front of me while she was peeing!"

Bathsturbate by stellaa165678 June 16, 2009

Bathsturbating 

The act of masturbating while in the bathtub.

"Dude, did you see that video that was leaked of Brittney Spears bathsturbating?"
"Yeah, dude, that was revolting!"

Bathsturbating by Thatonedefiniitionguy November 27, 2016