hallucination

noun
hal*lu*ci*na*tion \ hə-ˌlü-sə-ˈnā-shən \
1629{ds||1|a|}
  • a sensory perception (such as a visual image or a sound) that occurs in the absence of an actual external stimulus and usually arises from neurological disturbance (such as that associated with delirium tremens, schizophrenia, Parkinson's disease, or narcolepsy) or in response to drugs (such as LSD or phencyclidine)
  • the object of a hallucinatory perception
  • an unfounded or mistaken impression or notion : delusion
Powered by Merriam-Webster