1. an experience of seeing, hearing, or sensing something that is not actually present, often due to mental illness or drug use
Usage: medical; psychological
2. a false or mistaken belief or perception about something
Usage: figurative

Examples

• The patient experienced visual hallucinations as a side effect of the medication.
• Sleep deprivation can sometimes cause auditory hallucinations.
• His belief that he could become rich overnight was just a hallucination.
• The desert traveler’s vision of an oasis turned out to be a hallucination.
• Doctors determined that her hallucinations were symptoms of her condition.
• The idea that success comes without hard work is a dangerous hallucination.
• Certain drugs can trigger frightening hallucinations in users.