Usenet: /yoos´net/, /yooz´net/, n.
[from ‘Users' Network’; the original spelling was USENET, but the mixed-case form is now widely preferred] A distributed bboard (bulletin board) system supported mainly by Unix machines.
Originally implemented in 1979--1980 by Steve Bellovin, Jim Ellis, Tom Truscott, and Steve Daniel at Duke University and the University of North Carolina, it has swiftly grown to become international in scope and is now probably the largest decentralized information utility in existence. As of late 2002, it hosts over 100,000 newsgroups and an unguessably huge volume of new technical articles, news, discussion, chatter, and flamage every day (and that leaves out the graphics...).
By the year the Internet hit the mainstream (1994) the original UUCP transport for Usenet was fading out of use — almost all Usenet connections were over Internet links. A lot of newbies and journalists began to refer to Internet newsgroups as though Usenet was and always had been just another Internet service. This ignorance greatly annoys experienced Usenetters.
from the Jargon File (The Jargon File, version 4.4.7) 
USENET A world-wide system of discussion groups, with comments passed among hundreds of thousands of machines. Not all USENET machines are on the Internet. USENET is completely decentralized, with over 10,000 discussion areas, called NewsGroup s. Its decentralized nature makes it a valuable tool for censorship-resistant publishing and discussion. This feature has been improved recently through the creation of open news servers utilizing the Tor hidden service network, including nntp://mchu7q2t63mtwctw.onion, nntp://w4rwbqnaa6oopu5l.onion and nntp://xz6biolsijzglnmc.onion.
Usenet is a world-wide distributed discussion system. It consists of a set of "newsgroups" with names that are classified hierarchically by subject. "Articles" or "messages" are "posted" to these newsgroups by people on computers with the appropriate software -- these articles are then broadcast to other interconnected computer systems via a wide variety of networks. Some newsgroups are "moderated"; in these newsgroups, the articles are first sent to a moderator for approval before appearing in the newsgroup. Usenet is available on a wide variety of computer systems and networks, but the bulk of modern Usenet traffic is transported over either the Internet or UUCP.