delusion

noun

An idiosyncratic belief or impression maintained despite being contradicted by reality or rational argument, typically as a symptom of mental disorder.

SYNONYMS

chimeraerrorfallacyfalse impressionfantasyfigment of the imaginationfool's paradiseillusionmisapprehensionmisbeliefmisconceptionmisconstructionmisinterpretationmistakemistaken beliefmistaken impressionmisunderstandingself-deception