Formerly, a key Usenet and email
site, one that processes a large amount of third-party traffic,
especially if it is the home site of any of the regional
coordinators for the Usenet maps. Notable backbone sites as of
early 1993, when this sense of the term was beginning to pass out
of general use due to wide availability of cheap Internet
connections, included uunet and the mail machines at Rutgers
University, UC Berkeley, DEC's Western Research Laboratories,
Ohio State University, and the University of Texas. Compare
rib site, leaf site.
[1996 update: This term is seldom heard any more. The UUCP network
world that gave it meaning has nearly disappeared; everyone is on
the Internet now and network traffic is distributed in very
different patterns. Today one might see references to a `backbone
router' instead --ESR]
