Rather than refering to masturbation, the iron 5 knuckle pron shuffle refers to:
1)getting fisted by a large man/a group of men
2) getting completely obliterated by an obviously stronger person/force; Synonyms- Pwned, Owned, Destroyed
Guy 1 :So I was playing Ninja gaiden and-
Guy 2 : lemme guess, they did the iron five knuckle pron shuffle?
Guy 1 : I fucking hate you