Source : Free On-Line Dictionary of Computing

UUCPNET
     
        The international {store and forward} network consisting of
        all the world's connected {Unix} machines (and others running
        some clone of the {UUCP} software).  Any machine reachable
        only via a {bang path} is on UUCPNET.  See {network address}.
     
        [{Jargon File}]