1. Law. the crime of willfully inflicting a bodily injury on another so as to make the victim less capable of self-defense or, under modern statutes, so as to cripple or mutilate the victim.
2. random or deliberate violence or damage.
3. a state of rowdy disorder: Antagonisms between the various factions at the meeting finally boiled over, and mayhem ensued.
4. To Really do someone or something very bad, or very good