Critical hit

critical hit, n. 1. in certain RPG combat systems, a successful hit that does additional, aggravated, or fatal damage; usu. statistically improbable, or requiring expenditure of character resources.
Ex: You rolled "01" -- not only does your sword hit, but you decapitate him!
2. any successful combat or skill resolution that produces unexpected benefits. Also crit, critical success. See critical miss; see also lethal damage. [GJ1]