(Armor Class) (abbr.) 1. Armor Class. The higher the better, this is a measurement of the protective value provided by armour and various spells. e.g. "Wow - nice AC!" 2. Asheron's Call. Another massively multiplayer online role-playing game. Noted for larger customizability, and little-to-no zoning, fewer racial and class choices, and more roleplaying (in general).