gateway

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An opening or a structure framing an opening, such as an arch, that may be closed by a gate.
• noun Something that serves as an entrance or a means of access.
• noun Software or hardware that enables communication between computer networks that use different communications protocols.

from The Century Dictionary.

• noun A passage; an entrance; an opening which is or may be closed with a gate, as in a fence or wall.
• noun A frame or an arch in which a gate is hung: sometimes extended to the gate-house or gate-tower surmounting or flanking an entrance or a gate, and designed for ornament or defense.
• noun A means of ingress or egress generally—more frequently of ingress; an avenue; a passage; an approach.
• noun In coal-mining, same as gate.

from the GNU version of the Collaborative International Dictionary of English.

• noun 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An entrance capable of being blocked by use of a gate.
• noun Any point that represents the beginning of a transition from one place or phase to another.
• noun A point at which freight moving from one territory to another is interchanged between transportation lines.
• noun digital communications In wireless internet, an access point with additional software capabilities such as providing NAT and DHCP, which may also provide VPN support, roaming, firewalls, various levels of security, etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an entrance that can be closed by a gate