To log on to a machine or connect to a network
or BBS, esp. for purposes of entering a virtual reality
simulation such as a MUD or IRC (leaving is "jacking
out"). This term derives from cyberpunk SF, in which it was
used for the act of plugging an electrode set into neural sockets
in order to interface the brain directly to a virtual reality. It
is primarily used by MUD and IRC fans and younger hackers on BBS
systems.