The Free On-line Dictionary of Computing (30 December 2018):

Exterior Gateway Protocol
EGP

    (EGP) A protocol which distributes routing
   information to the routers which connect autonomous
   systems.

   The term "gateway" is historical, and "router" is currently
   the preferred term.

   There is also a routing protocol called EGP defined in STD
   18, RFC 904.

   See also Border Gateway Protocol, Interior Gateway
   Protocol.