Source : Free On-Line Dictionary of Computing

bamf
     
        /bamf/ 1. [Old X-Men comics] Notional sound made by a person
        or object teleporting in or out of the hearer's vicinity.
        Often used in {virtual reality} (especially {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}.
     
        [{Jargon File}]