Main Entry: lu·na·tic

Pronunciation: \ˈlü-nə-ˌtik\

Function: adjective

Etymology: Middle English lunatik, from Anglo-French or Late Latin; Anglo-French lunatic, from Late Latin lunaticus, from Latin luna; from the belief that lunacy fluctuated with the phases of the moon

Date: 14th century

1 a : affected with lunacy : insane b : designed for the care of insane persons <lunatic asylum>
2 : wildly foolish <a lunatic idea>

— lunatic noun