O.P. Meaning of O.P. in English 1. observation post. 2. Brit. Theat. See opposite prompt . 3. Order of Preachers (Dominican). [ Ordo Praedicatorum ] 4. out of print. 5. overproof. Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012