The sudden appearance of a security guard caused them to drop the money and run.
保安人员突然出现，他们丢下钱就跑了。
《牛津词典》
2
Don't drop your guard!
一定不要放弃你的卫生防护！
3
There are plenty of accidents and many overturned buses on a yearly basis. There are sheer drop offs of more than 1000 feet without a safety guard rail.