- To save this word, you'll need to log in.
  Log In

hallucination

noun

hal·lu·ci·na·tionhə-ˌlü-sə-ˈnā-shən How to pronounce hallucination (audio)

plural hallucinations

:a sensory perception (such as a visual image or a sound) that occurs in the absence of an actual external stimulus and usually arises from neurological disturbance (such as that associated with delirium tremens, schizophrenia, Parkinson's disease, or narcolepsy) or in response to drugs (such as LSD or phencyclidine)

visual/auditory/olfactory/gustatory/tactilehallucinations

a drug-inducedhallucination

An important aspect of the study ofhallucinations is the judgement of reality. How does a patient confer the character of reality on stimuli which, beyond any reasonable doubt, originate in his own mind?—

Cesare Davalli et al.

:the object of a hallucinatory perception

wasn't sure if the creature was real or ahallucination

:an unfounded or mistaken impression or notion:delusion

… that popularhallucination, from which not even great scientists are … free …—

Lewis Mumford

computing:a plausible but false or misleading response generated by an artificial intelligence algorithm

"This type ofartificial intelligence we're talking about can sometimes lead to something we callhallucination," said Prabhakar Raghavan in an interview with Germany's Welt am Sonntag newspaper published on Saturday. "This is then expressed in such a way that a machine delivers a convincing but completely fictitious answer."—

Matthew Broersma

Synonyms

See All Synonyms & Antonyms in Thesaurus

Choose the Right Synonym forhallucination

delusion,illusion,hallucination,mirage mean something that is believed to be true or real but that is actually false or unreal.

delusion implies an inability to distinguish between what is real and what only seems to be real, often as the result of a disordered state of mind.

delusions of persecution

illusion implies a false ascribing of reality based on what one sees or imagines.

anillusion of safety

hallucination implies impressions that are the product of disordered senses, as because of mental illness or drugs.

suffered from terrifyinghallucinations

mirage in its extended sense applies to an illusory vision, dream, hope, or aim.

claimed a balanced budget is amirage

Examples ofhallucination in a Sentence

He could not tell if what he was seeing was real or if it was ahallucination. He has been havinghallucinations due to the medication.

Recent Examples on the Web

Examples are automatically compiled from online sources to show current usage.Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.Send us feedback.

Ruiz’s father told San Antonio Express-News that his son had been exhibiting signs of a mental disorder, including havinghallucinationsand making paranoid accusations, in the days leading up to the stabbing.—

David Matthews,New York Daily News, 2 July 2025On Thursday, June 26, the father of 14-year-old Zane Wach shared an update on the teen's health following an incident two weeks ago, in which Zane began experiencinghallucinationsdue to what doctors believe was altitude sickness.—

Charlotte Phillipp,People.com, 29 June 2025Serious side effects are rare but need quick medical attention, including chest pain,hallucinations, or suicidal thoughts.—

Sarah Jividen,Verywell Health, 26 June 2025But in other cases, the model simply tried to cheat again—removing the markers the researchers used to detecthallucinations, even when the prompt the researchers used told the model explicitly not to do this.—

Jeremy Kahn,Fortune, 19 June 2025See All Example Sentences forhallucination

Word History

Etymology

seehallucinate

First Known Use

1629, in the meaning defined atsense 1a

Time Traveler

The first known use ofhallucination was in 1629

See more words from the same year

Rhymes forhallucination

See All Rhymes forhallucination

Browse Nearby Words

hallucinate

hallucination

hallucinatory

See all Nearby Words

Articles Related tohallucination

We Added 690 New Words to the...

Ngl, this update is a big one

Delusion vs. Hallucination: An...

Cite this Entry

Style

“Hallucination.”Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hallucination. Accessed 18 Jul. 2025.

Copy Citation

Kids Definition

hallucination

noun

hal·lu·ci·na·tionhə-ˌlüs-ə-ˈnā-shən How to pronounce hallucination (audio)

:the awareness of something (as a visual image, a sound, or a smell) that seems to be experienced through one of the senses but is not real, cannot be sensed by someone else, and is usually the result of mental illness or the effect of a drug

also:something of which one is aware but which is not real

Medical Definition

hallucination

noun

hal·lu·ci·na·tionhə-ˌlüs-ᵊn-ˈā-shən How to pronounce hallucination (audio)

:a sensory perception (as a visual image or a sound) that occurs in the absence of an actual external stimulus and usually arises from neurological disturbance (as that associated with delirium tremens, Lewy body disease, schizophrenia, Parkinson's disease, or narcolepsy) or in response to drugs (as LSD or phencyclidine)

visual/auditory/olfactory/gustatory/tactilehallucinations

a drug-inducedhallucination

comparedelusionsense 2,illusionsense 2a

:the object of a hallucinatory perception