The use of a potato peeler on a guy's dick. Very rare in real life, but nevertheless the ultimate potential downside of receiving a handjob or blowjob from a girl you just met. Often used as a joke at one of your homies after he turns a girl down.
Eg 1: Chris is kinda paranoid. This girl was going down on him when she pulled something out of her pocket; he freaked and thought she was gonna try potato peeling, but it was actually just her cell
Eg 2: why didn't you hook up with that girl? Afraid of potato peeling??