The Oxford Thesaurus An A-Z Dictionary of Synonyms - warrant n.

1) authorization, sanction, reason, justification, approval, validation, licence, right, certification, entitlement, grounds, cause, rationale, basis, assurance, carte blanche, guarantee, pledge, security, charter, warranty: We demand to know what warrant may exist for such an action. 2) writ, order, affidavit, paper, document, credential, permit, entitlement, licence, permit, summons, subpoena, mandate, decree, fiat, edict, ukase: Do not let them search the premises without a warrant. A warrant has been issued for her arrest. --v. 3) guarantee, promise, assure, ensure or insure, answer for, be answerable for, certify, vouch for, underwrite, back up, uphold, stand by or behind: All these products are warranted by the manufacturer for one year. 4) authorize, sanction, justify, explain, approve, verify, validate, permit, allow, provide or offer grounds or justification or cause or reason for, call for, necessitate, entitle, empower, excuse, license: What is it that warrants such accusations of malfeasance?