Beating someone or something senseless with a mechanical fist.
Oh man, I just got done power fisting, I'm exhausted. I think I'll go take a nap.
The act of repeatedly inserting and retracting a clenched fist at Bruce Lee speeds.
Usually into a bodily oraphis with out lube. If executed correctly uncontrollable bleeding will occur.
"I just got arrested for power fisting my girl friend, she got taken to ER"