on guard against

• adj. 警惕(提防)

on guard against的用法和样例：

例句

用作形容词 (adj.)

1. The dog kept a vigilant guard over the house.
   这只狗警惕地守护着这所房屋。
2. We must be on guard against hidden enemies.
   我们必须警惕暗藏的敌人。