The five knuckle shuffle is a slang term that refers to male masturbation.
Five Knuckle Shuffle
More About Five Knuckle Shuffle
The term five knuckle shuffle provides an innuendo to the movement that the hand makes during male masturbation. Though it is typically used to refer to solo masturbation, it has been used to refer to another individual doing the masturbation. It can be used to refer to a hand-job given by another person or mutual masturbation.