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

Internet Relay Chat
IRC

    (IRC) /I-R-C/, occasionally /*rk/ A
   client-server chat system of large (often worldwide)
   networks.  IRC is structured as networks of Internet
   servers, each accepting connections from client programs,
   one per user.

   The IRC community and the Usenet and MUD communities
   overlap to some extent, including both hackers and regular
   folks who have discovered the wonders of computer networks.
   Some Usenet jargon has been adopted on IRC, as have some
   conventions such as emoticons.  There is also a vigorous
   native jargon (see the entry for "chat").

   The largest and first IRC network is EFNet, with a smaller
   breakaway network called the Undernet having existed since
   1992, and dozens of other networks having appeared (and
   sometimes disappeared) since.

   See also nick, bot, op.

   Yahoo's IRC index
   (http://yahoo.com/Computers_and_Internet/Internet/Chat/IRC/).

   (1998-01-25)