Five Knuckle Shuffle is one of WWE Smackdown! Superstar John Cena's signature moves. He does his "You Can't See Me" then runs to the ropes, bounces against them, brushes his soldier then jumps down and punches you right in the face.
Cole: FIVE KNUCKLE SHUFFLE! And the pin...!
Masturbation: The phrase comes from the act of masturbating using the whole hand, wrapping 4 fingers round the shaft of the penis, and the thumb round the other side, hence "five knuckles".
Geordie 2: Ney chance. I was gannin' the Five knuckle shuffle till it felt like me hand'd fall off.
Most commonly used in pub-talks between men of age 18-30 to describe masturbation in a funny way, normally about someone, rather than themselves.