Definition: to give someone all the money you owe in one payment, rather than giving a small amount every week or month.
E.g.1: When her grandmother died she inherited £2,000 so she paid off her credit card debt and had enough money left for a short holiday.
E.g.2: If you don’t pay this debt off by the end of the month, I will have to contact my lawyer.
This phrasal verb can be separated (E.g. 2)