MOO Meaning of MOO in English /mooh/ , v. , mooed, mooing , n. , pl. moos . v.i.1. to utter the characteristic deep sound of a cow; low. n.2. a mooing sound. [ 1540-50; imit. ] Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012