OATER Meaning of OATER in English /oh"teuhr/ , n. Slang.a movie, television show, etc., about the frontier days of the U.S. West; western; horse opera. [ 1945-50; OAT + -ER 1 ] Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012