Medical Term
hallucination
also: hallucinations
a false perception of something that is not there, which may involve any of the senses of sight, hearing, smell, taste and touch. They may be caused by a psychological illness, e.g. SCHIZOPHRENIA . or damage to the brain, and also by certain drugs. They can also be a symptom of fever and deprivation, such as lack of sleep.
Source: mediLexicon corpus · slug
hallucination