From Longman Dictionary of Contemporary Englishat the mercy of somebody/somethingat the mercy of somebody/somethingCONTROLunable to do anything to protect yourself from someone or something After the boat’s motor failed, they were at the mercy of the weather. She was completely at his mercy. → mercy
Examples from the Corpus
at the mercy of somebody/something• With that relationship gone, they are at the mercy of more laws and more political meddling.• You are at the mercy of the man upstairs.• But like Jim, she soon found herself at the mercy of events.• Putting him at the mercy of men like you, Creller?• Once again Oliver is separated from his friends and left at the mercy of strangers.• Even compassion for a man so much at the mercy of his physical urges.• With monarchy, the essential problem is that power is put at the mercy of relatives and genetics.• He says you're at the mercy of the elements and you just go where the weather takes you.• Having lost engine power, the boat's crew found themselves at the mercy of the wind.• Ten miles straight up, at the mercy of bears, leopards and tigers. 