Merriam-Webster Collegiate Dictionary - warrant

 I. noun  Etymology: Middle English waraunt protector, ~, from Anglo-French warant, garant, of Germanic origin; akin to Old High German werento guarantor, weren to ~; akin to Old High German wara trust, care — more at very  Date: 14th century  1.  a.  (1) sanction, authorization; also evidence for or token of authorization  (2) guarantee, security  b.  (1) ground, justification  (2) confirmation, proof  2.  a. a commission or document giving authority to do something; especially a writing that authorizes a person to pay or deliver to another and the other to receive money or other consideration  b. a precept or writ issued by a competent magistrate authorizing an officer to make an arrest, a seizure, or a search or to do other acts incident to the administration of justice  c. an official certificate of appointment issued to an officer of lower rank than a commissioned officer  d.  (1) a short-term obligation of a governmental body (as a municipality) issued in anticipation of revenue  (2) an instrument issued by a corporation giving to the holder the right to purchase the stock of the corporation at a stated price either prior to a stipulated date or at any future time  • ~less adjective  II. transitive verb  Etymology: Middle English, waranten to act as protector, guarantee, from Anglo-French warentir, garantir, from warant  Date: 14th century  1.  a. to declare or maintain with certainty ; be sure that I'll ~ he'll be here by noon  b. to assure (a person) of the truth of what is said  2.  a. to guarantee to a person good title to and undisturbed possession of (as an estate)  b. to provide a guarantee of the security of (as title to property sold) usually by an express covenant in the deed of conveyance  c. to guarantee to be as represented  d. to guarantee (as goods sold) especially in respect of the quality or quantity specified  3. to guarantee security or immunity to ; secure I'll ~ him from drowning — Shakespeare  4. to give ~ or sanction to ; authorize the law ~s this procedure  5.  a. to give proof of the authenticity or truth of  b. to give assurance of the nature of or for the undertaking of ; guarantee  6. to serve as or give adequate ground or reason for promising enough to ~ further consideration