Repay is a verb that means to pay again or to return money that was borrowed. An antonym for repay is "default," which means to fail to fulfill an obligation, such as paying back a loan or debt. Another antonym for repay is "owe," which means that a debt or obligation still exists and has not yet been fulfilled. Additionally, "forgive" can be an antonym for repay due to the action of absolving a debt or obligation, meaning that the borrower is no longer required to pay it back. While repay typically implies fulfilling a financial obligation, its antonyms encompass the possibility of failing to comply with an agreement.