ETYM Latin delusio, from deludere. Related to Delude.
In psychiatry, a false belief that is unshakeably held. Delusions are a prominent feature of schizophrenia and paranoia, but may also occur in other psychiatric states.
1. A mistaken opinion or idea.
2. An erroneous belief that is held in the face of evidence to the contrary; SYN. psychotic belief.