[In the authors' words, "A weak pun on Multics"]

n. (also 'Unix') An interactive time-sharing system originally invented in 1969 by Ken Thompson after Bell Labs left the Multics project, originally so he could play games on his scavenged PDP-7. Dennis Ritchie, the inventor of C, is considered a co-author of the system. The turning point in UNIX's history came when it was reimplemented almost entirely in C during 1972--1974, making it the first source-portable OS. UNIX subsequently underwent mutations and expansions at the hands of many different people, resulting in a uniquely flexible and developer-friendly environment. In 1991, UNIX is the most widely used multiuser general-purpose operating system in the world. Many people consider this the most important victory yet of hackerdom over industry opposition (but see UNIX weenie and UNIX conspiracy for an opposing point of view).

See Version 7, BSD, USG UNIX.