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

That’s a lesson two California law firms learned this week when they were hit with $31,000 in sanctions for filing legal briefs citing non-existent cases that had been hallucinated by an LLM. —Alex Knapp, Forbes.com, 16 May 2025

OpenAI’s newest reasoning model, o3, released in April, seems to hallucinate more than twice as often as o1, according to the model card. —Hayden Field,jonathan Vanian,jennifer Elias, CNBC, 14 May 2025

Open source models hallucinated the most, with 21 percent of the dependencies linking to non-existent libraries. —Dan Goodin, ArsTechnica, 29 Apr. 2025

Read: The man out to prove how dumb AI still is To help temper—and harness—the tendency to hallucinate, newer AI systems are being positioned as collaborative tools that can help judge ideas. —Matteo Wong, The Atlantic, 25 Apr. 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