v. t. [ imp. & p. p. guaranteed p, pr. & vb. n. Guaranteeing. ] [ From Guarantee, n. ] In law and common usage: to undertake or engage for the payment of (a debt) or the performance of (a duty) by another person; to undertake to secure (a possession, right, claim, etc.) to another against a specified contingency, or in all events; to give a guarantee concerning; to engage, assure, or secure as a thing that may be depended on; to warrant; as, to guarantee the execution of a treaty. [ 1913 Webster ]

The United States shall guarantee to every State in this Union a republican form of government. Constitution of the U. S. [ 1913 Webster ]

n.; pl. Guarantees [ For guaranty, prob. influenced by words like assignee, lessee, etc. See Guaranty, and cf. Warrantee. ] 1. In law and common usage: A promise to answer for the payment of some debt, or the performance of some duty, in case of the failure of another person, who is, in the first instance, liable to such payment or performance; an engagement which secures or insures another against a contingency; a warranty; a security. Same as Guaranty. [ 1913 Webster ]

His interest seemed to be a guarantee for his zeal. Macaulay. [ 1913 Webster ]

2. One who binds himself to see an undertaking of another performed; a guarantor. South. [ 1913 Webster ]

☞ Guarantor is the correct form in this sense. [ 1913 Webster ]

3. (Law) The person to whom a guaranty is made; -- the correlative of guarantor.

Syn. -- Guarantee, Warranty. A guarantee is an engagement that a certain act will be done or not done in future. A warranty is an engagement as to the qualities or title of a thing at the time of the engagement. [ 1913 Webster ]

adj. 1. secured by written agreement.
Syn. -- bonded, secured, warranted. [ WordNet 1.5 ]

2. certified. [ WordNet 1.5 ]