Wiktionary
n. A role-playing game in which heroes navigate a labyrinthine environment, battling monsters and looting treasure.
Wikipedia
A dungeon crawl is a type of scenario in fantasy role-playing games in which heroes navigate a labyrinthine environment (a "dungeon"), battling various monsters, and looting any treasure they may find. Because of its simplicity, a dungeon crawl can be easier for a gamemaster to run than more complex adventures, and the " hack and slash" style of play is appreciated by players who focus on action and combat. The term can be used in a pejorative sense, since dungeon crawls often lack meaningful plot or logical consistency. The parody game Munchkin is about "the essence of the dungeon experience… Kill the monsters, steal the treasure, stab your buddy."
The first computer-based dungeon crawl was pedit5, developed in 1975 by Rusty Rutherford on the PLATO interactive education system based in Urbana, Illinois. Although this game was quickly deleted from the system, several more like it appeared, including dnd and Moria.
Some distinguish "dungeon crawlers" from rogue-likes and RPGs with stories and character-interaction, while others use the term to describe any game which features ample amounts of dungeon exploration (including Zork, Zelda and tabletop RPGs). More recently the term has come to mean 1st person RPGs, particularly ones which are aligned to a grid system and can be mapped on graph paper.