EMACS /ee'maks/ [from Editing MACroS] n. The ne plus ultra of hacker editors, a programmable text editor with an entire LISP system inside it. It was originally written by Richard Stallman in TECO under ITS at the MIT AI lab; AI Memo 554 described it as "an advanced, self-documenting, customizable, extensible real-time display editor". It has since been reimplemented any number of times, by various hackers, and versions exist that run under most major operating systems. Perhaps the most widely used version, also written by Stallman and now called "GNU EMACS" or GNUMACS, runs principally under UNIX. It includes facilities to run compilation subprocesses and send and receive mail; many hackers spend up to 80% of their tube time inside it. Other variants include GOSMACS, CCA EMACS, UniPress EMACS, Montgomery EMACS, jove, epsilon, and MicroEMACS.

Some EMACS versions running under window managers iconify as an overflowing kitchen sink, perhaps to suggest the one feature the editor does not (yet) include. Indeed, some hackers find EMACS too heavyweight and baroque for their taste, and expand the name as `Escape Meta Alt Control Shift' to spoof its heavy reliance on keystrokes decorated with bucky bits. Other spoof expansions include `Eight Megabytes And Constantly Swapping', `Eventually `malloc()'s All Computer Storage', and `EMACS Makes A Computer Slow' (see recursive acronym). See also vi.