(1) In Resource Access Control Facility (RACF), a string of one to eight characters that identifies a group. The first character must be A through Z, #, $, or @. The rest can be A through Z, #, $, @, or 0 through 9.
(2) In the AIX operating system, a number that corresponds to a specific group name. The group ID can often be substituted in commands that take a group name as a value.
(3) In the UNIX operating system, an integer that uniquely identifies each group of users to the operating system.