1 Experience a seemingly real perception of something not actually present, typically as a result of a mental disorder or of taking drugs.
1.1 with object Experience a hallucination of (something)
with clause ‘he starts hallucinating that he is Jesus’
Mid 17th century (in the sense ‘be deceived, have illusions’): from Latin hallucinat- ‘gone astray in thought’, from the verb hallucinari, from Greek alussein ‘be uneasy or distraught’.
Though others think him sleazy
And find he makes them queasy,
George, himself, finds it easy,
In his unstable state,
To regularly hallucinate
That he is really great!