The Collaborative International Dictionary of English v.0.48:

Gateway \Gate"way`\ (g[=a]t"w[=a]`), 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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gateway
    n 1: an entrance that can be closed by a gate

The Free On-line Dictionary of Computing (19 January 2023):

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 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)