noun de·lu·sion \di-ˈlü-zhən, dē-\

: a belief that is not true : a false idea

: a false idea or belief that is caused by mental illness

Full Definition of DELUSION

:  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
de·lu·sion·al \-ˈlüzh-nəl, -ˈlü-zhə-nəl\ adjective
de·lu·sion·ary \-zhə-ˌner-ē\ adjective

Origin of DELUSION

Middle English, from Late Latin delusion-, delusio, from deludere
First Known Use: 15th century

Synonym Discussion of DELUSION

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>.

Other Psychology Terms

fetish, hypochondria, intelligence, mania, narcissism, neurosis, pathological, psychosis, schadenfreude, subliminal
DELUSION Defined for Kids


noun de·lu·sion \di-ˈlü-zhən\

Definition of DELUSION for Kids

:  a false belief that continues in spite of the facts <“You might be laboring under the delusion that the entire … world is impressed with you …” — J. K. Rowling, Goblet of Fire>
Medical Dictionary


noun de·lu·sion \di-ˈlü-zhən\

Medical Definition of DELUSION

a :  the act of deluding :  the state of being deluded b :  an abnormal mental state characterized by the occurrence of psychotic delusions
:  a false belief regarding the self or persons or objects outside the self that persists despite the facts and occurs in some psychotic states—compare hallucination 1, illusion 2a


Next Word in the Dictionary: delusionistPrevious Word in the Dictionary: delundungAll Words Near: delusion
How to use a word that (literally) drives some people nuts.
Test your vocab with our fun, fast game
Ailurophobia, and 9 other unusual fears