Easton's Bible Dictionary

Probably the same as epileptic, the symptoms of which disease were supposed to be more aggravated as the moon increased. In Matthew 4:24 "lunatics" are distinguished from demoniacs. In 17:15 the name "lunatic" is applied to one who is declared to have been possessed. (see DAEMONIAC.)

Noah Webster's New International Dictionary of the English Language

1. (n.) An insane person.

2. (a.) of or pertaining to, or suitable for, an insane person; evincing lunacy; as, lunatic gibberish; a lunatic asylum.

3. (n.) A person affected by lunacy; an insane person, esp. one who has lucid intervals; a madman; a person of unsound mind.