an act or instance of deluding.

the state of being deluded.

a false belief or opinion

delusions of grandeur.

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

a paranoid delusion.

noun

actuality , certainty , fact , reality , surety , truth , disenchantment , disillusionment

noun

apparition , blunder , casuistry , chicanery , daydream , deception , deceptiveness , dream , eidolon , error , fallacy , false impression , fancy , fantasy , figment * , fool’s paradise , ghost , hallucination , head trip , ignis fatuus , illusion , lapse , mirage , misapprehension , mistake , optical illusion , oversight , phantasm , phantom , pipe dream * , self-deception , shade , speciousness , spuriousness , trickery , trip , visionnotes:allusion is an \'indirect mention , \' illusion is \'false impression , [[\' and delusion is \'deception\' which is much stronger than illusionhallucination is from disturbed sensory perceptions; delusion is from disturbed thinkingan illusion is an image or conception of something actual or real that presents itself to the mind in an abnormal or distorted manner; a delusion is a false belief about oneself or other people that persists despite its being at variance with the facts]] , phantasma , will-o\'-the-wisp , aberration , figment , mare\'s nest , misconception , mockery , ruse , trick , vision , wishful thinking