劍橋詞典 RR (TRAIN) written abbreviation for railroad noun 鐵路，鐵道（railroad的縮寫） RR (POST) written abbreviation for rural route : used in addresses in some areas in the US 鄉(xiāng)村郵件投遞路線（用于美國(guó)鄉(xiāng)村地區(qū)通信地址中，rural route的縮寫） RR (BREATHING) medical specialized written abbreviation for respiratory rate (= the rate at which someone breathes in and out) 呼吸頻率（respiratory rate的縮寫） 返回 RR