Internet Relay Chat
<chat, messaging> (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://www.yahoo.com/Computers_and_Internet/Internet/Chat/IRC/).