APA Dictionary of Psychology

a parasomnia in which an individual partially awakens during NREM sleep, appears fully awake but is unresponsive to or exhibits impaired orientation to environmental stimuli, and has no memory afterward for events occurring during an episode. Individuals experiencing a severe episode may become aggressive toward others or self-injurious. Confusional arousal is especially common in children but can occur in adults as well. Also called sleep disorientation; sleep drunkenness; somnolentia.