固若金湯 [ㄍㄨˋ ㄖㄨㄛˋ ㄐㄧㄣ ㄊㄤ; gu4 ruo4 jin1 tang1] secure as a city protected by a wall of metal and a moat of boiling water (idiom) well fortified invulnerable to attack ◄ ►
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