hallucination

noun

hal·​lu·​ci·​na·​tion hə-ˌlü-sə-ˈnā-shən 

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

Synonyms

• chimera
• conceit
• daydream
• delusion
• dream
• fancy
• fantasy
• phantasy
• figment
• illusion
• nonentity
• phantasm
• fantasm
• pipe dream
• unreality
• vision

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

Weak from blood loss, the 13-year-old wasn’t sure what was real and what was hallucination. —Marisa Kwiatkowski, USA TODAY, 14 May 2024

As this intersection continues to be explored, the new paper raises the possibility that such medical benefits could be achieved without the hallucinations. —Christian Thorsberg, Smithsonian Magazine, 10 May 2024

Research has found that smaller A.I. systems could be more likely to make errors, known as hallucinations, than larger ones. —Cade Metz, New York Times, 10 May 2024

Advertisement In this way, Chambers’ nonprofit functions as a third space for the local community, especially those who dabble in psychedelics — substances like psilocybin (magic mushrooms), peyote, ayahuasca, DMT, LSD, ketamine and MDMA — that affect the mind and often cause hallucinations. —Renée Reizman, Los Angeles Times, 8 May 2024

LLMs are also capable of hallucinating; while humans also make errors, AI hallucinations may be more egregious and may be more likely to cause harm. —Adam Rodman, STAT, 3 May 2024

Symptoms progress and become more severe as time goes on, which includes cerebral disfunction, anxiety, confusion, agitation, delirium, abnormal behavior, hallucinations, hydrophobia and insomnia. —Amaris Encinas, USA TODAY, 3 May 2024

And the bot occasionally provides bizarre answers, known as hallucinations in AI models, that can spread misinformation about public health. —Jessica Nix, Fortune Europe, 19 Apr. 2024

It is associated with hallucinations, delusions, and extremely disordered thinking and behavior that impairs daily functioning, and can be disabling. —Vanessa Etienne, Peoplemag, 16 Apr. 2024

Word History

Etymology

see hallucinate

First Known Use

1629, in the meaning defined at sense 1a

Kids Definition

hallucination

noun

hal·​lu·​ci·​na·​tion hə-ˌlüs-ə-ˈnā-shən 

: 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·​tion hə-ˌlüs-ᵊn-ˈā-shən 

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