hallucinate

verb

hal·​lu·​ci·​nate hə-ˈlü-sə-ˌnāt 

hallucinated; hallucinating

transitive verb

1

: to affect with visions or imaginary perceptions

2

: to perceive or experience as a hallucination

intransitive verb

: to have hallucinations

hallucinator

hə-ˈlü-sə-ˌnā-tər 

noun

Examples of hallucinate in a Sentence

The patient may hallucinate if she has a fever.

Recent Examples on the Web

But the tendency for large language models to hallucinate or make errors is a big potential problem in healthcare, especially on the clinical side where people’s lives are involved. —Amy Feldman, Forbes.com, 21 Jan. 2026

What if a person was hallucinating, and a voice told them to commit the crime? —Literary Hub, 20 Jan. 2026

Plus, multiple studies suggest that if there’s missing information in your medical records, models are more likely to hallucinate, or produce incorrect or misleading results. —Angela Haupt, Time, 9 Jan. 2026

Chen says their models hallucinate far less than traditional LLMs and already match state-of-the-art performance in time-series forecasting tasks like weather prediction, quantitative trading, and medical monitoring. —Eva Roytburg, Fortune, 28 Nov. 2025

Word History

Etymology

Latin hallucinatus, past participle of hallucinari, allucinari to prate, dream, modification of Greek alyein to be distressed, to wander

First Known Use

circa 1834, in the meaning defined at transitive sense 1

Kids Definition

hallucinate

verb

hal·​lu·​ci·​nate hə-ˈlüs-ə-ˌnāt 

hallucinated; hallucinating

: to have hallucinations or experience as a hallucination

Medical Definition

hallucinate

verb

hal·​lu·​ci·​nate hə-ˈlüs-ᵊn-ˌāt 

hallucinated; hallucinating

transitive verb

1

: to affect with visions or imaginary perceptions

the patient is not hallucinated

2

: to perceive or experience as a hallucination

may hallucinate monsters or attackers

—M. J. Horowitz

intransitive verb

: to have hallucinations