Source : Free On-Line Dictionary of Computing

Internet backbone
     
         High-speed networks that carry
        {Internet} traffic.
     
        These {communications} {networks} are provided by companies
        such as {AT&T}, {GTE}, {IBM}, {MCI}, {Netcom}, {Sprint},
        {UUNET} and consist of high-speed links in the {T1}, {T3},
        {OC1} and {OC3} ranges.  The {backbones} carry {Internet}
        traffic around the world and meet at {Network Access Points}
        (NAPs).
     
        {Internet Service Providers} (ISPs) connect either directly to
        a backbone, or they connect to a larger ISP with a connection
        to a backbone.
     
        The {topology} of the "backbone" and its interconnections may
        once have resembled a spine with ribs connected along its
        length but is now almost certainly more like a fishing net
        wrapped around the world with many circular paths.
     
        [Map?]
     
        (1998-07-02)