Source : Webster's Revised Unabridged Dictionary (1913)

Gateway \Gate"way`\, n.
   A passage through a fence or wall; a gate; also, a frame,
   arch, etc., in which a gate in hung, or a structure at an
   entrance or gate designed for ornament or defense.

Source : WordNet®

gateway
     n : an entrance that can be closed by a gate

Source : Free On-Line Dictionary of Computing

gateway
     
        1.  A deprecated term for a device that enables
        data to flow between different networks (forming an
        {internet}).
     
        Preferred terms are "{protocol converter}" (connects networks
        that use different {protocols}), "{router}" (connects two
        broadcast networks at layer 3 ({network layer}).  Another
        example is a {mail gateway}, which is a layer 7 ({application
        layer}) gateway.
     
        2.  An {interface} between an information source
        and a {World-Wide Web} {server}.  {Common Gateway Interface}
        is a {standard} for such interfaces.  The information source
        can be any system that can be accessed by a program running on
        the web server.  A typical example is a {relational
        database}.
     
        (2000-05-24)