n.1. a cognitive distortion in which an individual views a single event as an invariable rule, so that, for example, failure at accomplishing one task will predict an endless pattern of defeat in all tasks. 2. the process of extending something beyond the circumstances to which it actually applies. It is a common linguistic tendency of young children to generalize standard grammatical rules to apply to irregular words (e.g., pluralizing foot to foots). See overextension; overregularization.