Slevening A Head Clean Off Edit Meaning

1.

When you take a 35mm film canister of the movie "Lucky Number Slevin", and unravel the film to a confortable length in between your two fists, and then you use the sharp edge of the fimstock to slice someone else's head off their body.

Hey Bobby, look what that man over there is doing. He is Slevening a head clean off!