銅墻鐵壁（銅牆鐵壁）　

◎ 銅墻鐵壁 tóngqiáng-tiěbì

[bastion of iron,impregnable fortress as a wall of bronze;impregnable like walls of brass and iron] 亦作“鐵壁銅墻”,比喻防御工事堅(jiān)固,也比喻力量的強(qiáng)大、意志的堅(jiān)定