extra; free addition; bonus

Explanation

1. extra; free addition; bonus
The act of adding extra for free to a product that has been paid for; or such an extra item.

2. free; for nothing
What is left over or gained for free beyond one's rightful share.

Examples
덤을 주다
덤으로 더 주다
덤으로 얹어 주다

7 more sentences in the app — free account.