hallucination

American  

[huh-loo-suh-ney-shuhn] / həˌlu səˈneɪ ʃən /

noun

• hallucinations
  plural

1. a sensory experience of something that does not exist outside the mind, caused by various physical and mental disorders, or by reaction to certain toxic substances, and usually manifested as visual or auditory images.

   Synonyms:

   aberration, phantasm

2. the sensation caused by a hallucinatory condition, or the object or scene visualized.

3. a false notion, belief, or impression; illusion; delusion.

4. Computers, Digital Technology. (in the field of machine learning) false information generated by a machine learning program contrary to the intent of the user and presented as if it were true and factual.

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hallucination British  

/ həˌluːsɪˈneɪʃən /

noun

1. the alleged perception of an object when no object is present, occurring under hypnosis, in some mental disorders, etc

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hallucination Cultural  

1. A false perception that appears to be real, as when, for example, a man dying of thirst in a desert thinks that he sees a lake. (See also delusion.)

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Usage

What is a hallucination? A hallucination is a sensory experience of something that does not actually exist and has no basis in reality. Hallucinations can be caused by mental disorders or toxic substances. A hallucination often takes the form of visual images or noises, as in Sangeet saw a hallucination of sparkling lights. Hallucination can also be used to refer to the sensation caused by one of these false sensory experiences, as in Roman was suffering from drug-induced hallucinations. More generally, hallucination can be used to mean a false notion or belief, as in His idea of what life was like in Canada was nothing more than a silly hallucination. Hallucination is similar to the words illusion and delusion, which also describe false beliefs or experiences. An illusion is a false image that is a result of a distortion or manipulation of actual things. For example, makeup can create the illusion that a person is younger than they actually are. A delusion is a persistent, false belief that may or may not be partially based on reality, as in The athlete’s huge ego constantly made him have delusions of being unbeatable. Example: The explorer suffered from terrifying hallucinations of ghosts and phantoms after eating the toxic mushrooms.

Synonym Usage

See illusion.

Other Word Forms

Derived Forms

• nonhallucination
  noun
• hallucinational
  adjective
• hallucinative
  adjective

Inflected Forms

Nouns

• hallucinations
  plural

Etymology

Origin of hallucination

First recorded in 1640–50; from Latin hallūcinātiōn-, stem of hallūcinātiō, variant of (h)ālūcinātiō, “a wandering of the mind”; hallucinate + -ion

Explanation

If you see your teacher morph into a dancing elephant, chances are you’re having a hallucination, or an illusory perception. In other words, it sounds like you are seeing things! A person experiencing a hallucination perceives things that aren’t really there. A hallucination can involve any of the senses — including sight, hearing, touch, smell, and taste — and often results from a mental disorder or a chemical source, such as a drug.

Example Sentences

See Examples For:

hallucination hallucinations

“In an experience like this, you’re alone with the inhabitants of the world, and they’re all there as part of your hallucination, your dream and your journey,” Neiden says.

From Los Angeles Times ● Sep. 18, 2026

An episode is prison slang for a severe hallucination.

From Slate ● Aug. 11, 2026

“The GPT 5.6 series tends to ground itself in real data when doing knowledge work. It’s better at citing where that data came from. It’s a little more reliable on the hallucination front,” he said.

From MarketWatch ● Jul. 17, 2026

Despite improvements, AI models still vary in hallucination frequency, leading to misinformation and user “cognitive surrender.”

From The Wall Street Journal ● Apr. 14, 2026

Seconds later, the wagon door swings open, and the forbidding walls of Blackcliff are before me, their oppressive weight driving the hallucination from my mind.

From "An Ember in the Ashes" by Sabaa Tahir

Tony’s hallucinations might be open to psychiatric interpretation, but Dick’s are true, as well as dramatically strategic: Craziness like Tony’s is only so interesting.

From The Wall Street Journal ● Sep. 17, 2026

Hypnopompic hallucinations are what specialists call the unreal things people see or hear during the transition from sleep to waking.

From The Wall Street Journal ● Sep. 15, 2026

Kusama said she saw hallucinations of dots and lights as a child, and used those visions in her art from the 1960s.

From BBC ● Aug. 27, 2026

The "polka dot queen" channelled hallucinations and battles with mental health into vibrant art featuring her trademark dots, nets and infinity motifs over a career spanning decades and continents.

From Barron's ● Aug. 27, 2026

Were there other things I had thought were hallucinations, but were actually real?

From "Made You Up" by Francesca Zappia

Related Words

• illusion
• phantom