I. a person who takes responsibility for another's performance of an undertaking, for example their appearing in court or the payment of a debt. ii. money given to support an undertaking that someone will perform a duty, pay their debts, etc.; a guarantee. 1. "the judge granted bail with a surety of $500" iii. a surety bond or surety is a promise by a surety or guarantor to pay one party (the obligee) a certain amount if a second party (the principal) fails to meet some obligation, such as fulfilling the terms of a contract.