What you say before partaking in the act of you and a friend making "the horns" with your hands and then bumping knuckles by turning one pair of horns vertical and one horizontal, making a recreation of animals butting horns. This is used as a greeting, or to drunkenly celebrate a win.
dude whats up! Clash em!
that was awesome! Clash em!
whats up ya fuckin faggot? clash em!
hey you dirtsack, clash em!