delusion

Noun

• the act of deluding; deception by creating illusory ideas

• a mistaken or unfounded opinion or idea
  • he has delusions of competence
    
  • his dreams of vast wealth are a hallucination
    

• (psychology) an erroneous belief that is held in the face of evidence to the contrary

Related words

• Synonyms: 
  illusion , head game , hallucination , psychotic belief