n. 1. a. The act or process of deluding. b. The state of being deluded. 2. a. A false belief or opinion: labored under the delusion that success was at hand. b. Psychiatry A false belief or perception that is a manifestation of a mental illness: delusions of persecution. [Middle English delusioun, from Latin dēlūsiō, dēlūsiōn-, from dēlūsus, past participle of dēlūdere, to delude; see DELUDE.] de·lusion·al adj. |
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