Source : Free On-Line Dictionary of Computing

traceroute
     
        A (typically Unix) {TCP/IP} utility which allows the user to
        determine the {route} {packet}s are taking to a particular
        {host}.  Traceroute works by increasing the "{time to live}"
        value of packets and seeing how far they get, until they reach
        the given destination; thus, a lengthening trail of hosts
        passed through is built up.