A verbal altercation, usually between wannabe alpha-males, as each one tries to out-do the other in terms of being more cool/trendy/tough/hard/fly et cetera. The attitude is typically in your face; fortunately, each male is usually surrounded by enough of his friends who can hold him back for the sake of the other guy should things threaten to get physical. In fact, he may have to ask them to do so, purely for the other guy's safety, of course.
In effect, what each is trying to convey is "my penis is bigger than yours" while hoping they will not be called on it. It would probably be easier for each involved guy to drop his pants before the argument starts and just give the victory to the most well-endowed of them.
In most cases nothing comes of it at all, and each male retires to his circle of friends claiming to have won.
Guy #1: I'll hit you so hard you'll have to walk three blocks to find your face!
Guy #2: Please! I'll hit you so hard your family will die.
Guy #1: Yeah? You and whose army?
Guy #2: You're lucky these guys are holding me back!
Random bystander: This is a complete cockshow - nothing's going to happen. Let's go somewhere else.