1. To give compensation, financial or otherwise, to one for some service one rendered or debt one is owed. I'd really like to repay you somehow for all the help you gave me on my research. It'll be years before I'm able to repay them for the loan they gave me.

2. To do something that exhibits or indicates a complete lack of gratitude, regard, or esteem for one. (Sarcastic or ironic in its use.) It just sickens me that you would do something so contemptible to me. Is this how you repay me for devoting my life to your upbringing? Sarah sacrificed a lot in order to be with Tom, and he repaid her for her loyalty by cheating on her for the entirety of their relationship.

3. To seek revenge or retribution for one's actions. I'm going to slash the principal's tires to repay him for humiliating me in front of my class. Now that our rebellion is sufficiently armed, we are finally ready to repay this dictatorship for the brutal and heinous crimes it has committed against its people.