LOONY Meaning of LOONY in English n. & adj. sl.n. (pl. -ies) a mad or silly person; a lunatic. adj. (loonier, looniest) crazy, silly. loony-bin sl. a mental home or hospital. looniness n.[ abbr. of LUNATIC ] Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012