guaranty

from The American Heritage® Dictionary of the English Language, 5th Edition.

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

from The Century Dictionary.

• Same as guarantee.
• noun The act of warranting or securing; a warrant or surety.
• noun Specifically, in law, a separate, independent contract by which the guarantor undertakes, in writing, for a valuable consideration, to be answerable for the payment of some particular debt, or future debts, or the performance of some duty, in case of the failure of another person primarily liable to pay or perform. Colebrooke, On Collateral Securities.
• noun That which guarantees anything; a ground or basis of security: as, constitutional guaranties; his character is guaranty for his assertions; what guaranty have I that you will keep your word?

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb In law and common usage: To undertake or engage that another person shall perform (what he has stipulated); to undertake to be answerable for (the debt or default of another); to engage to answer for the performance of (some promise or duty by another) in case of a failure by the latter to perform; to undertake to secure (something) to another, as in the case of a contingency. See guarantee, v. t.
• noun In law and common usage: An undertaking to answer for the payment of some debt, or the performance of some contract or duty, of another, in case of the failure of such other to pay or perform; a guarantee; a warranty; a security.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun law An undertaking to answer for the payment of some debt, or the performance of some contract or duty, of another, in case of the failure of such other to pay or perform; a warranty; a security.
• noun Something serving as a security for such an undertaking.
• noun An assurance or guarantee.
• verb Obsolete spelling of guarantee.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a collateral agreement to answer for the debt of another in case that person defaults