Glossary » side effects
actions that occur as the result of a user action which do not seem to the user to be related to the primary goal of the action. For instance, when starting a game changes system configurations (such as screen and sound settings) and fails to change it back when the game is not being used.
Side effects should be avoided. They cause particular problems for novice users and disabled users who may have difficulty detecting or correcting certain types of side effects.