铜墙铁壁 Traditional 銅牆鐵壁 tóng qiáng tiě bì 🔊 copper wall, iron bastion (idiom) + Keep this word Meanings tóng qiáng tiě bì 銅牆鐵壁 copper wall, iron bastion (idiom); impenetrable defense Its characters 铜tóngcopper (chemistry)HSK 6墙qiángwall (CL:面[mian4],堵[du3])HSK 5铁tiěiron (metal)HSK 7–9壁bìwall