delirium
n. a disturbed mental state in which attention cannot be sustained, the environment is misperceived, and the stream of thought is disordered. The individual may experience changes in cognition (which can include disorientation, memory impairment, or disturbance in language), perceptual disturbances, hallucinations, illusions, and misinterpretation of sounds or sights. The episode develops quickly and can fluctuate over a short period. Delirium may be caused by a variety of conditions, such as infections, cerebral tumors, substance intoxication and withdrawal, head trauma, and seizures.