- Subjectively experienced sensations in the absence of an appropriate stimulus, but which are regarded by the individual as real. They may be of organic origin or associated with mental disorders.
Definition from: MeSH via Unified Medical Language System at the National Library of Medicine
- Perceptions through any sense modality in the absence of an appropriate stimulus. (Usually indicative of abnormality but may be experienced occasionally by normal persons).
Definition from: Psychological Index Terms via Unified Medical Language System at the National Library of Medicine
- A hallucination is a false sensory perception in the absence of an external stimulus, as distinct from an illusion which is a misperception of an external stimulus. (from Wikipedia)
Definition from: NCI Thesaurus via Unified Medical Language System at the National Library of Medicine
- 1: A perception of something (as a visual image or a sound) with no external cause usually arising from a disorder of the nervous system (as in delirium tremens or in functional psychosis without known neurological disease) or in response to drugs (as LSD).
2: The object of a hallucinatory perception.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
See also Understanding Medical Terminology.