delusional
UK: dɪˈluːʒənəl | US: dɪˈluːʒənəl
adj. holding false or irrational beliefs despite evidence to the contrary
adj. relating to or characteristic of a delusion
The word "delusional" stems from the Latin deludere ("to deceive"), combining de- (thoroughly) + ludere (to play, mock). Over time, "delusion" evolved in Late Latin (delusio) to mean "a deceiving," later narrowing to "fixed false belief" in English. The suffix -al (from Latin -alis) transforms the noun into an adjective, describing someone influenced by such beliefs. The progression reflects a shift from playful deception to pathological irrationality.
His delusional claims about being a king alarmed his family.
The therapist diagnosed her with delusional disorder.
It’s delusional to think you can win without practice.
The cult leader’s delusional prophecies misled many followers.
She laughed off his delusional conspiracy theories.