큰돈 (keundon) means “a large sum of money”

More examples

그 일로 큰돈을 벌었어요.keu il lo keun do neul peo reo sseo yo

I made a large sum of money from that job.

A sizable amount of money that stands out in an ordinary financial situation.

목돈moktton: A lump sum saved and kept ready for a major expense.
많은 돈maneun ton: A large quantity of money described in everyday language.

비격식에서 자주 쓰이는 비교적 큰 금액을 가리키는 말pi gyeok ssi ge seo cha ju sseu i neun pi gyo jeok keun keu mae geul ka ri ki neun mal

Its meaning comes transparently from the combination of the Korean modifier for big and the native Korean noun for money.

The word describes the speaker's sense of scale rather than a fixed amount, and that scale depends on the situation.