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

“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

Scaled Cognition addresses AI hallucination with a model that predicts structured objects, such as programs and system queries, in addition to token streams.

From The Wall Street Journal ● Jun. 25, 2026

Yet, it was no hallucination to see Vin Diesel strutting the red carpet in a custom blazer with rhinestones spelling out “Fast Forever,” the 11th and final installment, scheduled to be released in 2028.

From Los Angeles Times ● May 15, 2026

"We're in a state of hallucination," says Éva Bognár, a researcher at the Central European University's Democracy Institute.

From BBC ● Apr. 4, 2026

“Edda,” I introduced myself, wondering somehow if this was all really happening, or whether exhaustion from my travels was causing an elaborate hallucination.

From "The Brightwood Code" by Monica Hesse

When colleagues raise concerns over its accuracy and hallucinations, Glazer said the point that always hits home is reminding them that while AI isn’t perfect, neither are the junior professionals who work for them.

From The Wall Street Journal ● Jul. 8, 2026

“You see these articles about firms being sanctioned because they have hallucinations in their court filings. And the reaction of someone who’s already hesitant is, ‘Gee, I can’t do that,’” Glazer said.

From The Wall Street Journal ● Jul. 8, 2026

I was in awe of the fact that in 40 years of reporting on the White House I never once, in my wildest and most macabre hallucinations, dreamed up anything like that event.

From Salon ● Jun. 19, 2026

Charlotin has been compiling a database of court documents containing AI hallucinations since April 2023.

From Barron's ● Jun. 15, 2026

In the absence of key nutrients, a severe chemical imbalance develops in the brain, inducing convulsions and hallucinations.

From "Into the Wild" by Jon Krakauer

Related Words

• illusion
• phantom