Source : Free On-Line Dictionary of Computing

Interior Gateway Protocol
     
        (IGP) An {Internet} {protocol} which distributes {routing}
        information to the {router}s within an {autonomous system}.
        The term "{gateway}" is historical, "router" is currently the
        preferred term.
     
        See also {Exterior Gateway Protocol}, {Open Shortest Path
        First}, {Routing Information Protocol}.
     
        (1994-11-09)