:xor: /X'or/, /kzor/ conj. Exclusive or. `A xor B' means `A or B, but not both'. "I want to get cherry pie xor a banana split." This derives from the technical use of the term as a function on truth-values that is true if exactly one of its two arguments is true.
:xref: /X'ref/ vt., n. Hackish standard abbreviation for `cross-reference'.
:XXX: /X-X-X/ n. A marker that attention is needed. Commonly used in program comments to indicate areas that are kluged up or need to be. Some hackers liken `XXX' to the notional heavy-porn movie rating.
:xyzzy: /X-Y-Z-Z-Y/, /X-Y-ziz'ee/, /ziz'ee/, or /ik-ziz'ee/ [from the ADVENT game] adj. The {canonical} `magic word'. This comes from {ADVENT}, in which the idea is to explore an underground cave with many rooms and to collect the treasures you find there. If you type `xyzzy' at the appropriate time, you can move instantly between two otherwise distant points. If, therefore, you encounter some bit of {magic}, you might remark on this quite succinctly by saying simply "Xyzzy!" "Ordinarily you can't look at someone else's screen if he has protected it, but if you type quadruple-bucky-clear the system will let you do it anyway." "Xyzzy!" Xyzzy has actually been implemented as an undocumented no-op command on several OSes; in Data General's AOS/VS, for example, it would typically respond "Nothing happens", just as {ADVENT} did if the magic was invoked at the wrong spot or before a player had performed the action that enabled the word. In more recent 32-bit versions, by the way, AOS/VS responds "Twice as much happens". See also {plugh}.
= Y = =====
:YA-: [Yet Another] abbrev. In hackish acronyms this almost invariably expands to {Yet Another}, following the precedent set by UNIX `yacc(1)' (Yet Another Compiler-Compiler). See {YABA}.
:YABA: /ya'b*/ [Cambridge] n. Yet Another Bloody Acronym. Whenever some program is being named, someone invariably suggests that it be given a name that is acronymic. The response from those with a trace of originality is to remark ironically that the proposed name would then be `YABA-compatible'. Also used in response to questions like "What is WYSIWYG?" See also {TLA}.
:YAUN: /yawn/ [Acronym for `Yet Another UNIX Nerd'] n. Reported from the San Diego Computer Society (predominantly a microcomputer users' group) as a good-natured punning insult aimed at UNIX zealots.
:Yellow Book: [proposed] n. The print version of this Jargon File; `The New Hacker's Dictionary', MIT Press, 1991 (ISBN 0-262-68069-6). Includes all the material in the 2.9.6 version of the File, plus a Foreword by Guy L. Steele Jr. and a Preface by Eric S. Raymond. Most importantly, the book version is nicely typeset and includes almost all of the infamous Crunchly cartoons by the Great Quux, each attached to an appropriate entry.
:yellow wire: [IBM] n. Repair wires used when connectors (especially ribbon connectors) got broken due to some schlemiel pinching them, or to reconnect cut traces after the FE mistakenly cut one. Compare {blue wire}, {purple wire}, {red wire}.