gateway

n. entrance, portal; passage; computer which connects two networks (Computers)

n. American corporation headquartered in California, manufacturer and distributor of personal computer systems and related equipment

Gateway has several meanings. It may often share meanings with the term gate.
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Noun
1. an entrance that can be closed by a gate
(hypernym) entrance, entranceway, entryway, entry, entree

(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.
  

1. In a communications network, a network node equipped for interfacing with another network that uses different protocols. (188 ) Note 1: A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. It also requires that mutually acceptable administrative procedures be established between the two networks. Note 2: A protocol translation/mapping gateway interconnects networks with different network protocol technologies by performing the required protocol conversions. 2. Loosely, a computer configured to perform the tasks of a gateway.