hallucination
    n 1: illusory perception; a common symptom of severe mental
         disorder
    2: a mistaken or unfounded opinion or idea; "he has delusions of
       competence"; "his dreams of vast wealth are a hallucination"
       [syn: delusion, hallucination]
    3: an object perceived during a hallucinatory episode; "he
       refused to believe that the angel was a hallucination"

Hallucination \Hal*lu`ci*na"tion\ (-n[=a]"sh[u^]n), n. [L.
   hallucinatio: cf. F. hallucination.]
   1. The act of hallucinating; a wandering of the mind; error;
      mistake; a blunder.
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            This must have been the hallucination of the
            transcriber.                          --Addison.
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   2. (Med.) The perception of objects which have no reality, or
      of sensations which have no corresponding external cause,
      arising from disorder of the nervous system, as in
      delirium tremens; delusion.
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            Hallucinations are always evidence of cerebral
            derangement and are common phenomena of insanity.
                                                  --W. A.
                                                  Hammond.
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HALLUCINATION, med. jur. It is a species of mania, by which "an idea 
reproduced by the memory is associated and embodied by the imagination." 
This state of mind is sometimes called delusion or waking dreams. 
     2. An attempt has been made to distinguish hallucinations from 
illusions; the former are said to be dependent on the state of the 
intellectual organs and, the latter, on that of those of sense. Ray, Med. 
Jur. Sec. 99; 1 Beck, med. Jur. 538, note. An instance is given of a 
temporary hallucination in the celebrated Ben Johnson, the poet. He told a 
friend of his that he had spent many a night in looking at his great toe, 
about which he had seen Turks and Tartars, Romans and Carthagenians, fight, 
in his imagination. 1 Coll. on Lun. 34. If, instead of being temporary, this 
affection of his mind had been permanent, he would doubtless have been 
considered insane. See, on the subject of spectral illusions, Hibbert, 
Alderson and Farrar's Essays; Scott on Demonology, &c.; Bostock's 
Physiology, vol. 3, p. 91, 161; 1 Esquirol, Maladies Mentales, 159.