jack in

jack in v.  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.