hallucination

noun

hal·​lu·​ci·​na·​tion hə-ˌlü-sə-ˈnā-shən How to pronounce hallucination (audio)
plural hallucinations
1
a
: 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/tactile hallucinations
a drug-induced hallucination
An important aspect of the study of hallucinations 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.
b
: the object of a hallucinatory perception
wasn't sure if the creature was real or a hallucination
2
: an unfounded or mistaken impression or notion : delusion
… that popular hallucination, from which not even great scientists are … free … — Lewis Mumford
3
computing : a plausible but false or misleading response generated by an artificial intelligence algorithm
"This type of artificial intelligence we're talking about can sometimes lead to something we call hallucination," 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
Choose the Right Synonym for hallucination

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.

an illusion of safety

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

suffered from terrifying hallucinations

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

claimed a balanced budget is a mirage

Examples of hallucination in a Sentence

He could not tell if what he was seeing was real or if it was a hallucination. He has been having hallucinations due to the medication.
Recent Examples on the Web His defense attorney argued during the preliminary hearing in Chula Vista Superior Court last year that her client may have been suffering from mental health issues and experiencing hallucinations or delusions. City News Service, San Diego Union-Tribune, 12 Mar. 2024 Siebel acknowledged the catalog of concerns that companies now have with generative AI—random responses, lack of traceability, no data controls, increased cyber risk, IP exposure, hallucinations. Alan Murray, Fortune, 7 Mar. 2024 Critics warn that LLMs may pose subtler problems than hallucinations. David Berreby, Scientific American, 20 Feb. 2024 Wilson has long suffered from mental health issues, including depression, anxiety, bipolar disorder and schizoaffective disorder, with the latter known to cause hallucinations, paranoia and distorted reality. Gil Kaufman, Billboard, 16 Feb. 2024 As Navarro and Danvers investigate, Navarro is plagued by hallucinations and flashbacks to her time serving in combat overseas — the same breaks from reality haunting her younger sister Julia (Aka Niviâna). Alison Herman, Variety, 5 Feb. 2024 Mice exposed to checkerboard patterns went on to daydream of the motifs, the auras perceived by migraine sufferers are not only visual but include auditory and gustatory hallucinations, and reindeer brain waves revealed that rumination can be a form of sleep. Elizabeth Barber, Harper's Magazine, 2 Feb. 2024 The result is wide variability among providers, with some favoring gradual, low-dosage treatments while others advocate larger amounts that can induce hallucinations, as the drug is psychedelic at the right doses. Dawn Megli | Kff Health News, ABC News, 31 Jan. 2024 The most common symptoms of psychosis, regardless of cause, are delusions (false beliefs) and hallucinations (seeing or hearing things that aren’t there). Katie Camero, USA TODAY, 31 Jan. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'hallucination.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

see hallucinate

First Known Use

1629, in the meaning defined at sense 1a

Time Traveler
The first known use of hallucination was in 1629

Dictionary Entries Near hallucination

Cite this Entry

“Hallucination.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hallucination. Accessed 19 Mar. 2024.

Kids Definition

hallucination

noun
hal·​lu·​ci·​na·​tion hə-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 disorder 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·​tion hə-ˌlüs-ᵊn-ˈā-shən How to pronounce hallucination (audio)
1
: 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/tactile hallucinations
a drug-induced hallucination
compare delusion sense 2, illusion sense 2a
2
: the object of a hallucinatory perception
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