ADVENT /ad'vent/ n.
The prototypical computer adventure game, first designed by Will Crowther on the PDP-10 in the mid-1970s as an attempt at computer-refereed fantasy gaming, and expanded into a puzzle-oriented game by Don Woods at Stanford in 1976. (Woods had been one of the authors of INTERCAL.) Now better known as Adventure or Colossal Cave Adventure, but the TOPS-10 operating system permitted only six-letter filenames. See also vadding, Zork, and Infocom.
This game defined the terse, dryly humorous style since expected in text adventure games, and popularized several tag lines that have become fixtures of hacker-speak: "A huge green fierce snake bars the way!" "I see no X here" (for some noun X). "You are in a maze of twisty little passages, all alike." "You are in a little maze of twisty passages, all different." The `magic words' xyzzy and plugh also derive from this game.
Crowther, by the way, participated in the exploration of the Mammoth & Flint Ridge cave system; it actually has a `Colossal Cave' and a `Bedquilt' as in the game, and the `Y2' that also turns up is cavers' jargon for a map reference to a secondary entrance.
ADVENT sources are available for FTP at ftp://ftp.wustl.edu/doc/misc/if-archive/games/source/advent.tar.Z. There is a Colossal Cave Adventure page.