[ dih-loo-zhuhn ]
See synonyms for: delusiondelusions on

  1. an act or instance of deluding.

  2. the state of being deluded.

  1. a false belief or opinion: delusions of grandeur.

  2. Psychiatry. a fixed false belief that is resistant to reason or confrontation with actual fact: a paranoid delusion.

Origin of delusion

First recorded in 1375–1425; late Middle English, from Latin dēlūsiōn- (stem of dēlūsiō ), equivalent to dēlūs(us) (past participle of dēlūdere; see delude) + -iōn- -ion

synonym study For delusion

1. See illusion.

Other words for delusion

Other words from delusion

  • de·lu·sion·al, de·lu·sion·ar·y, adjective
  • pre·de·lu·sion, noun

Words that may be confused with delusion

Words Nearby delusion Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use delusion in a sentence

British Dictionary definitions for delusion


/ (dɪˈluːʒən) /

  1. a mistaken or misleading opinion, idea, belief, etc: he has delusions of grandeur

  2. psychiatry a belief held in the face of evidence to the contrary, that is resistant to all reason: See also illusion, hallucination

  1. the act of deluding or state of being deluded

Derived forms of delusion

  • delusional, adjective
  • delusive, adjective
  • delusively, adverb
  • delusiveness, noun
  • delusory (dɪˈluːsərɪ), adjective

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for delusion


[ dĭ-lōōzhən ]

  1. A false belief or perception strongly held in spite of invalidating evidence, especially as a symptom of mental illness, as in schizophrenia.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for delusion


A false belief held despite strong evidence against it; self-deception. Delusions are common in some forms of psychosis. Because of his delusions, the literary character Don Quixote attacks a windmill, thinking it is a giant.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.