noun
a sensory perception that has no basis in external reality, typically as a result of a mental disorder or the effects of a drug
-
The patient experienced a visual hallucination, seeing things that were not actually there.
-
I thought I saw a ghost last night, but it turned out to be just a hallucination.
-
Don't worry, it was just a hallucination, you're not going crazy.
-
The mirage in the desert was like a hallucination, appearing and disappearing in the heat.