hallucination

hallucination is a Noun

Definition:

[1] The act of hallucinating; a wandering of the mind; error; mistake; a blunder. This must have been the hallucination of the transcriber. Addison.

[2] The perception of objects which have no reality, or of sensations which have no corresponding external cause, arising from disorder or the nervous system, as in delirium tremens; delusion. Hallucinations are always evidence of cerebral derangement and are common phenomena of insanity. W. A. Hammond.