defences
n. 防御工事（defence 复数）
例句
These front-line defences are backed up by armoured units in reserve.
前线防御有后备装甲部队的支援。
《柯林斯英汉双解大词典》
The democracies of the West may find it hard to shore up their defences.
西方的民主国家可能发现很难加固自己的防御。
The harbour's sea defences are in poor condition.
港口的海防工事状况很差。
《牛津词典》
