2) The act of slamming ones crotch into ones face/mouth/crotch/back of skull
3) An act of rage
Frank: I hung out with Nicole.
Dave: What did you guys do?
Frank: I was fucking slam dancing between her legs.
However there is less actual violence in a slam dancing crowd, and the occasional meathead in one can ruin it for eveyone.
Skanking in a mosh is either being way too confident for your own good or suidical.
"so what man, get a bunch of people together and start slam dancing"