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.
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
Lewis Mumford3
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
Matthew BroersmaSynonyms
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
Knowledge graphs: • Ensure LLMs pull from factual data, helping to improve accuracy and reduce hallucinations.
—Brian Platz, Forbes, 21 Nov. 2024
Factual accuracy is another issue for AI agents, since they’re built on LLMs that have a problem with hallucinations—the technical term for making things up.
—IEEE Spectrum, 19 Nov. 2024
Nair believes that integrating AI into her company is nonnegotiable, but plans to introduce measures to address biases and hallucinations that continue to plague the technology.
—Sasha Rogelberg, Fortune, 30 Oct. 2024
But be warned: Apple is reportedly still working on preventing AI hallucinations.
—Emily Dreibelbis Forlini, PCMAG, 28 Oct. 2024
See all Example Sentences for hallucination 
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Brian Platz, Forbes, 21 Nov. 2024
Factual accuracy is another issue for AI agents, since they’re built on LLMs that have a problem with hallucinations—the technical term for making things up.
—IEEE Spectrum, 19 Nov. 2024
Nair believes that integrating AI into her company is nonnegotiable, but plans to introduce measures to address biases and hallucinations that continue to plague the technology.
—Sasha Rogelberg, Fortune, 30 Oct. 2024
But be warned: Apple is reportedly still working on preventing AI hallucinations.
—Emily Dreibelbis Forlini, PCMAG, 28 Oct. 2024
See all Example Sentences for hallucination
Articles Related to hallucination
Dictionary Entries Near hallucination
Cite this Entry
“Hallucination.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/hallucination. Accessed 30 Nov. 2024.
Copy CitationKids 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
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