A promise to be answerable for the debt or obligation of another in the event of nonpayment or nonperformance. Something given as security for the execution, completion, or existence of something else. The act of providing such security. A guarantee, as for a product or service: a new refrigerator still under guaranty. A guarantee to perform something in a specified way. A guarantee serving to assure a particular outcome or condition. A guarantor. To provide a guaranty for. To guarantee.