The fear that the guy next to you at a urinal is masturbating. This accounts for urinals, stalls, and sinks in both male and femal bathrooms. The act is usually done vigorously, loud, and with a mean finish, or quiet, calm, and discreetly.
Dude: Let's stop by the house, I gotta use the bathroom.
Dude2: Why can't you just go here?
Dude: I have masturinalphobia.....
Dude2: Dude no one's going to do anything wierd.
Dude: You ever heard of Peewee Herman?
Dude2: We'll stop by your house.