/tekh/
n. An extremely powerful macro-based text formatter written by Donald E. Knuth, very popular in the computer-science community (it is good enough to have displaced UNIX 'troff(1)', the other favored formatter, even at many UNIX installations). TeX fans insist on the correct (guttural) pronunciation, and the correct spelling (all caps, squished together, with the E depressed below the baseline; the mixed-case 'TeX' is considered an acceptable kluge on ASCII-only devices). Fans like to proliferate names from the word 'TeX' -- such as TeXnician (TeX user), TeXhacker (TeX programmer), TeXmaster (competent TeX programmer), TeXhax, and TeXnique.
Knuth began TeX because he had become annoyed at the declining quality of the typesetting in volumes I-III of his monumental 'Art of Computer Programming' (see bible). In a manifestation of the typical hackish urge to solve the problem at hand once and for all, he began to design his own typesetting language. He thought he would finish it on his sabbatical in 1978; he was wrong by only about 8 years. The language was finally frozen around 1985, but volume IV of 'The Art of Computer Programming' has yet to appear as of mid-1991. The impact and influence of TeX's design has been such that nobody minds this very much. Many grand hackish projects have started as a bit of tool-building on the way to something else; Knuth's diversion was simply on a grander scale than most.