Definition of: delusion

(di·l′zhən) noun
1. The state of being deluded; a false belief, especially when persistent.
2. The act of deluding; deception.
3. The error thus conveyed or believed.
4. Psychiatry False belief about the self, often present in paranoia and dementia precox. [<L delusio, -onis <deludere. See DELUDE.] Synonyms: error, fallacy, fantasm, hallucination, illusion. A delusion is a mistaken conviction, an illusion a mistaken perception or inference. An illusion may be wholly of the senses; a delusion always involves some mental error. We speak of the illusions of fancy or of hope, but of the delusions of the insane. A hallucination is a false image or belief which has nothing, outside of the disordered mind, to suggest it; as, the hallucinations of delirium tremens. Compare DECEPTION. Antonyms: actuality, certainty, fact, reality, truth, verity.