noun /həˌluːsəˈneɪʃən/
a) A sensory perception of something that does not exist, arising from disorder of the nervous system, as in delirium tremens; a delusion.
, Hallucinations are always evidence of cerebral derangement and are common phenomena of insanity. - W. A. Hammond
, This must have been the hallucination of the transcriber. -
Wikipedia foundation.