n.[C]

1. （護城）城堡；堡壘，要塞
2. 安全的地方；避難處
3. （軍艦上的）炮塔
   The invading warplane dropped a bomb which destroyed the citadel of the frigate.

   來襲的飛機丟下一顆炸彈，炸毀了軍艦上的炮塔。

n.

1. a fortress protecting or dominating a city.
2. a meeting hall of the Salvation Army.