One who agrees to pay a debt. Cosigning is often used when one party has poor credit or no credit. If that person can’t or won’t pay, the cosigner is on the hook for the outstanding debt. Under the Credit CARD Act of 2009, anyone under age 21 must have an adult cosigner on a credit card account or show proof that they have enough income on their own to repay the debt. Credit card companies must stay at least 1,000 feet from college campuses, if they are offering free pizza or other gifts to entice students to apply for credit cards.