hallucination (hah-lu”si-na'shun) [L. hallucinatio; Gr. alyein to wander in the mind] a sense perception without a source in the external world; a perception of an external stimulus object in the absence of such an object. auditory h., the hearing of unreal sounds. depressive h., hallucinations occurring in the course of acute depression. gustatory h., a hallucination of taste. haptic h., a tactile hallucination. hypnagogic h., a hallucination occurring between sleeping and awakening. lilliputian h., a hallucination in which things seem smaller than they actually are. olfactory h., hallucination of smell. reflex h., arousal of a secondary sensation by a sensation of a different modality. stump h., phantom limb. tactile h., hallucination of touch. visual h., a sensation of seeing not stimulated by actual presence of the object seen.
— Dorland's Illustrated Medical Dictionary, Twenty-fifth Edition (W.B. Saunders, 1974)