Butt Rock is otherwise known as an "arena-ready anthem." The sounds are repetitious, the voices tend to be raspy and often loud, and the lyrics typically consist of either nonsense or kicking someone's ass.
The music is called "Butt Rock" due to the fact that the music sounds like an anal release passing through an oboe with electric guitar and vocals sprinkled in.
To make it easy on your self, just watch an episode of WWE and listen to the "Butt Rock" entrance music. You will know it when you hear it.
Dammit, that wrestler has another one of those Butt Rock entrances.