Note put in a poker pot when one runs out of money

• Written promise to pay
• Note in a pot
• Promissory note, of a sort
• Gambler's promise, abbr
• Simple promissory note
• Bettor's slip
• Note from a short person
• Letters signifying debt
• Letters preceding a number

Wikipedia Word definitions in Wikipedia
An IOU (abbreviated from the phrase "I owe you") is usually an informal document acknowledging debt . An IOU differs from a promissory note in that an IOU is not a negotiable instrument and does not specify repayment terms such as the time of repayment. ...