a. [ Shortened fr. lunatic. ] 1. Crazy; insane; lunatic; mentally unsound. [ Low, U.S. ] [ Written also loony, luny and looney. ] See Luny. [ 1913 Webster ]
2. Very foolish; very impractical; as, loony ideas. [ PJC ]
pos>n. An institution for the confinement or treatment of insane persons, such as an insane asylum or the psychiatric ward of a hospital. [ slang ] Syn. -- mental institution. [ PJC ]