1) v. to pledge or agree to be responsible for another's debt or contractual performance if that other person does not pay or perform. Usually, the party receiving the guarantee will first try to collect or obtain performance from the debtor before trying to collect from the one making the guarantee (guarantor). 2) the promise to pay another's debt or fulfill contract obligations if that party fails to pay or perform. 3) n. occasionally, the person to whom the guarantee is made. 4) a promise to make a product good if it has some defect.