citadel [ˈsɪtədəl, -ˌdɛl]

例句:

• The citadel was solid.
  城堡是坚固的.
  
• The business is no longer regarded as a citadel of commerce.
  该行业不再被视为贸易的堡垒。
  
• He died for Germany in the gigantic and futile operation called Citadel.
  他在被称为“城堡”行动的一次大规模的劳而无功的战役中阵亡.
  
• To collect all the remaining strength...in a mountain citadel.
  来自C. Thirlwall
• The university figured as the citadel of conservatism.
  来自L. Trilling
• The French had had to evacuate their troops from the citadel in Aleppo.
  来自W. S. Churchill