hypersomnia /hī′pərsom″nē·ə/ [Gk, hyper + L, somnus, sleep] , 1. sleep of excessive depth or abnormal duration, usually caused by psychological rather than physical factors and characterized by a state of confusion on awakening. 2. extreme drowsiness, often associated with lethargy. 3. a condition characterized by periods of deep, long sleep. Compare narcolepsy.
