DictionarylunaticMental instability
noun

lunatic

A dated, offensive term for a person considered mentally unstable.

The old medical record describes the patient as a lunatic.

Etymology

The Latin adjective reflects an old belief that the moon could cause mental disturbance. That mistaken association produced a person-name now regarded as dated and offensive.

More examples

  • The museum explains why doctors no longer call patients lunatics.
  • She objects to the offensive label “lunatic.”
  • The historian examines an old law concerning people classified as lunatics.

Forms

lunatic · lunatics

lunacy noun — A dated, offensive term for mental instability.

Similar words

madman
Also dated and offensive; specifically identifies the person as male.
madwoman
Also dated and offensive; specifically identifies the person as female.