lunatic

A person who is affected by lunacy; a mentally deranged person.

A very foolish person.

Affected by lunacy; mentally deranged.

Of or for people who are mentally deranged.

Wildly or giddily foolish.

Moonstruck; affected by lunacy; periodically insane, with lucid intervals; crazy.

Indicating lunacy; in the nature of lunacy.

Of or like the moon.

A person affected with lunacy; specifically, an insane person who has lucid intervals, or one whose unsoundness of mind is acquired, not congenital, as distinguished from an idiot.

More generally (and in law), any person of unsound mind. See further under lunacy and insanity.