Source : Free On-Line Dictionary of Computing

multicast backbone
     
        (MBONE) A {virtual network} on top of the {Internet} which
        supports {routing} of {IP} {multicast} {packet}s, intended for
        {multimedia} transmission.  MBONE gives public access {desktop
        video} communications.  The quality is poor with only 3-5
        frames per second instead of the 30 frames per second of
        commercial television.  Its advantage is that it avoids all
        telecommunications costs normally associated with
        teleconferencing.  An interesting innovation is the use of
        MBONE for audio communications and an electronic "whiteboard"
        where the computer screen becomes a shared workspace where two
        physically remote parties can draw on and edit shared
        documents in {real-time}.
     
        (1994-10-27)