固若金湯 [－－－汤]

Jyutping gu3 joek6 gam1 tong1
Pinyin gù ruò jīn tāng

Definitions (CC-CEDICT)
  1. secure as a city protected by a wall of metal and a moat of boiling water (idiom)
  2. well fortified
  3. invulnerable to attack
Definitions (Wiktionary)
  1. phrase, idiomatic
    strongly fortified; impregnable
Examples (粵典–words.hk)
  1. Cantonese
    固若金汤
    固若金湯
    gu3 joek6 gam1 tong1
    • impregnable; unassailable