1. （因生病或吸毒所致的）幻觉（体验）
A hallucination is the experience of seeing something that is not really there because you are ill or have taken a drug.

2. （因生病或吸毒所见到的）幻象
A hallucination is something that is not real that someone sees because they are ill or have taken a drug.

1. an object perceived during a hallucinatory episode

e.g. he refused to believe that the angel was a hallucination

2. a mistaken or unfounded opinion or idea

e.g. he has delusions of competence
his dreams of vast wealth are a hallucination

Synonym: delusion

3. illusory perception
a common symptom of severe mental disorder