Synonyms for Hallucination:

n.

fantasy, optical illusion, a figment of your imagination, fraud, imaginings. chill, perforation, aetiology, crisis, etiology, Phantasma, real, pathology, discharge, Ignis Fatuus, mirage, complication, dehydration. phantasmagoria, Phantasmagory, trip. dream, delusion (noun)
fantasy, mirage, phantasmagoria, trip.
hallucination (noun)
delusion.
illusion (noun)
dream, study at illusion, mirage.
insanity (noun)
dementia, psychosis, insanity, madness, delirium, brain-sickness, lunacy, kookiness, feverishness, neurosis, craziness, nuttiness, derangement, mania, battiness, frenzy.
psychical research (noun)
fortune telling, psychology, divination, mysticism, necromancy, telepathy, astrology, hypnotism, psychoanalysis, soothsaying, hysteria, spiritualism, psychotherapy, sorcery, supernaturalism.

Other synonyms:

Ignis Fatuus, optical illusion, phantasmagoria, Phantasmagory. complication, etiology, fraud, pathology. crisis, dehydration, perforation, Phantasma. trip. discharge, chill. illusion
mirage.
Other relevant words:
delusion, perforation, fraud, mirage, crisis, trip, Ignis Fatuus, Phantasma, etiology, pathology, chill, Phantasmagory, dream, optical illusion, phantasmagoria, fantasy.

Usage examples for hallucination

  1. The difference between illusion and hallucination is sometimes imperceptible; the same is sometimes true of legend and myth. – Essay on the Creative Imagination by Th. Ribot
  2. Very well, then; I make all possible allowances for your strange hallucination – The British Barbarians by Grant Allen
  3. Whoever the visitor was, it was not a subjective hallucination on the part of Mr. Dickinson. – Real Ghost Stories by William T. Stead