hallucination
n.n. a feeling or image that you see, hear, or feel in your mind when there is nothing there. It is like seeing or hearing something that is not real.
n. a sensory perception that occurs without any external stimulus. It is often used to describe a mental state where a person experiences sights, sounds, or sensations that are not present in reality.
He had a hallucination of hearing his mother's voice.
The patient reported a vivid hallucination of a bright light in the room, though no one else saw it.
In the final stages of the illness, the patient experienced complex hallucinations that blurred the line between memory and reality, making it difficult for caregivers to provide consistent support.
Derives from the verb hallucinate, from Latin hallucinatus. Compare French hallucination. The first known usage in the English language is from Sir Thomas Browne.