Etymology: Middle English, from Late Latin delusion-, delusio, from deludere
Date: 15th century
1. the act of deluding ; the state of being deluded
a. something that is falsely or delusively believed or propagated
b. a persistent false psychotic belief regarding the self or persons or objects outside the self that is maintained despite indisputable evidence to the contrary; also the abnormal state marked by such beliefs
• delusional adjective
• delusionary adjective
delusion, illusion, hallucination, mirage mean something that is believed to be true or real but that is actually false or unreal. delusion implies an inability to distinguish between what is real and what only seems to be real, often as the result of a disordered state of mind <delusions of persecution>. illusion implies a false ascribing of reality based on what one sees or imagines <an illusion of safety>. hallucination implies impressions that are the product of disordered senses, as because of mental illness or drugs <suffered from terrifying hallucinations>. mirage in its extended sense applies to an illusory vision, dream, hope, or aim <claimed a balanced budget is a mirage>.
New Collegiate Dictionary. 2001.