1. [from old X-Men comics] interj. Notional sound made by a person or object teleporting in or out of the hearer's vicinity. Often used in virtual reality (esp. MUD) electronic fora when a character wishes to make a dramatic entrance or exit.
2. The sound of magical transformation, used in virtual reality fora like sense 1.
3. [from 'Don Washington's Survival Guide'] n. Acronym for 'Bad-Ass Mother Fucker', used to refer to one of the handful of nastiest monsters on an LPMUD or other similar MUD.