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

For example, OpenAI’s 03 and 04-mini models hallucinate—that is, makes up its own answers to questions—around 30 to 50% of the time, per the company’s own recent tests. —Victoria Feng, Forbes.com, 15 July 2025

Did Martin’s outburst finally convince Masha that hallucinating the ghosts of your past isn’t the healthiest way to deal with loss? —Rafaela Bassili, Vulture, 2 July 2025

When LLMs hallucinate, the consequences can be spectacular. —Gabriel Snyder, MSNBC Newsweek, 25 June 2025

Once Player 96 is knocked off the bridge by the rope, other players — including Min-su, who is hallucinating after taking his last pill — are able to cross. —Jennifer Zhan, Vulture, 27 June 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