Definition of "Unix"

(computing) An operating system that shares the original source code by Dennis Ritchie and Ken Thompson, currently owned by Novell.  examples

(computing) An operating system largely compatible with Unix that qualifies for use of the UNIX trademark, currently owned by The Open Group.  examples

(computing, informal) Any of the above plus Unix-like operating systems similar to Unix but not qualifying for use of the UNIX trademark.  examples