Definitions

1. noun

A promissory note, especially one given by a customer to a merchant.

“The customer gave the store an IOU for the purchased item.”

2. noun

A note or written promise to repay a debt.

“She wrote an IOU to her brother for the borrowed money.”

3. verb

To give or repay something, especially a debt, in a future time.

“He will IOU his friend for the loaned book.”