Definition - What does UNIX 93 mean?
UNIX 93 is an Open Group Specification compatible with many UNIX based specifications, including XPG3, XPG4, SVID and AT&T source code. In 1996, UNIX 93 was terminated by X/Open.
Techopedia explains UNIX 93
UNIX is an OS formulated in 1969 at Bell Labs as an interactive time-sharing system. It was never a proprietary OS and is not owned by the leading computer companies. UNIX also is written in a standard language and is comprised of many popular ideas, which led UNIX to become the primary available open standard OS.