1. A fistfight where the odds are stacked highly in one of the two participants favours, commonly resulting in broken bones and softening of the face.
2. The climax of a hardcore song, usually a down-tempo combination of palm muted open strings/extensive pinch harmonics and low end chords, where crowd participant's can quite simply unleash the beast on one another.
3. fucking awesome.
"Did you see that fight outside the bar last night?"
"Mate, that wasn't even a fight, poor guy just got a serious beatdown"
"Have you heard Nasty's new album???"
"Yeah, when i heard the beatdown on track 4 i thought i was going to void my bowels"