group identifier

from The Free On-line Dictionary of Computing (8 July 2008)

group identifier

   <operating system> (gid) A unique number, between 0 an 32767,
   identifying a set of {users} under {Unix}.  Gids are found in
   the /etc/{passwd} and /etc/group databases (or their {NIS}
   equivalents) and one is also associated with each file,
   indicating the group to which its group {permissions} apply.

   (1996-12-01)