hallucinate

verb

hal·​lu·​ci·​nate hə-ˈlü-sə-ˌnāt 

hallucinated; hallucinating; hallucinates

transitive verb

1

: to affect with visions or imaginary perceptions

2

: to perceive or experience as a hallucination

3

of artificial intelligence : to produce (output) that is false or misleading

OpenAI says this training makes the output of its model safer, more relevant and less likely to "hallucinate" facts.

—JoElla Carman and Jasmine Cui

intransitive verb

1

: to have hallucinations

2

of artificial intelligence : to create false or misleading output

Inaccurate facts are included, thanks to the AI chatbot hallucinating.

—Rachel Kane

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

Finally, validate all information is correct rather than hallucinated. — Expert Panel®, Forbes.com, 20 Aug. 2026

Wolff is direct about the fact that AI can hallucinate and requires constant oversight. — Ethan M. Stone, USA Today, 18 Aug. 2026

The cybersecurity firm Palo Alto Networks recently studied websites at domain names whose URLs are frequently hallucinated by AI chatbots, discovering at some of these sites a range of malware and other malicious code. — David Berreby, IEEE Spectrum, 13 Aug. 2026

This can lead to real-life negative results, like poor investment decisions based on viewing incorrect financial information hallucinated by large language models. — Joshua Hong, Fortune, 7 Aug. 2026

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

1652, in the meaning defined at intransitive 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