Critical miss

critical miss, n. 1. in certain RPG combat systems, a failed to hit roll that produces catastrophic results for the character; usu. statistically improbable.
Ex: You rolled "00" -- not only does your sword miss, but you cut off your own leg! 2. any failed combat or skill resolution that produces catastrophic results beyond the mere failure of the attempt. Also fumble, botch, critical failure, catastrophic miss. See critical hit, DoubleZodd. [GJ1]
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Addendum: Critical fumbles or misses are generally standard in most games (In D&D they're optional). The game that inspires the most fear when it comes to critical fumbles however, is Rolemaster. Its' critical fumble charts are nasty, covering any situation from magic miscast to fumble with edged melee weapon. Many critical fumbles end with “instant death” or some gruesome variation.
Addendum #2: Our DM loved the Rolemaster charts so much he used them for our D&D game. They were stored in a green binder, and any time someone rolled a critical fumble, the entire table groaned when the DM brought the “binder of doom” out. He, of course, later converted it to a program run on his laptop, speeding up the painful process.