1. 潜伏的危险：a smooth face 一副讨好面孔 | a snake in the grass 潜伏的危险 | a soldier of fortune 兵痞

2. 隐患：a dog in the manger.占着毛坑不拉屎的人. | a snake in the grass.隐患. | like a donkey between two bundles of hay.优柔寡断.

3. 潜伏的敌人：a dark horse 实力难测的竞争者 | a snake in the grass 潜伏的敌人 | an early bird 早起的人

4. 极其阴险的人：金盆洗手to wash one's hands of sth. | 极其阴险的人a snake in the grass | 我听说/有人私下告诉我a little bird told me