hallucination

n. vision, imaginary perception, delusion

A hallucination is a perception in the absence of a stimulus that is believed to be genuine, ie. the subject experiences an imaginary stimulus as being real. A pseudohallucination is similar to an hallucination in all respects except that of absolute belief in the authenticity of the stimulus. In an illusory experience, a genuine sensation is attributed to an incorrect cause (eg. misinterpreting a coat hanging on a door to be an intruder). A delusional perception is where a genuine perception (ie. correctly sensed and interpreted) is given some additional (and typically bizarre) significance. Hallucinations may occur in any sensory modality—visual, auditory, olfactory, gustatory, tactile, proprioceptive, equilibrioceptive, nociceptive, thermoceptive.
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Hallucination /hal·lu·ci·na·tion/ a sense perception that has no basis in external stimulation.hallu´cinativehallu´cinatory haptic hallucination [more]Hallucination - Community and Resources

Noun
1. illusory perception; a common symptom of severe mental disorder
(hypernym) delusion, psychotic belief
(hyponym) auditory hallucination, acousma
(derivation) hallucinate
2. a mistaken or unfounded opinion or idea; "he has delusions of competence"; "his dreams of vast wealth are a hallucination"
(synonym) delusion
(hypernym) misconception
(hyponym) disorientation, freak out
(derivation) hallucinate
3. an object perceived during a hallucinatory episode; "he refused to believe that the angel was a hallucination"
(hypernym) object
(derivation) hallucinate

n. hallucination, vision, imaginary perception