Legal Definition of Guaranty: (a) A statement by a producer that his product meets certain standards, and that if it proves to be defective, he will make restitution; a warranty. (b) To undertake the responsibility of paying someone’s debt should he fail to pay it himself | Find out what a guaranty is and its importance in building trust between businesses and consumers. Learn how offering a guaranty can enhance a business’s reputation, give a competitive advantage, and foster customer loyalty. Discover how guaranties provide assurance to customers that the products they purchase will meet specific standards of quality and performance