To pay back money that is owed to someone. She promised to repay the loan by the end of the month.
To return a favor or kindness. He wanted to repay her for all the help she had given him.
To retaliate or respond to an action with a similar action. He vowed to repay the insult with a clever comeback.
To be worth the time, effort, or cost invested; to reward by yielding value or satisfaction. The documentary repays repeated viewings.