The Collaborative International Dictionary of English v.0.48:

Warrant \War"rant\, v. t. [imp. & p. p. Warranted; p. pr. &
   vb. n. Warranting.] [OE. waranten, OF. warantir, garantir,
   guarantir, garentir, garandir, F. garantir to warrant, fr.
   OF. warant, garant, guarant, a warrant, a protector, a
   defender, F. garant. [root]142. See Warrant, n.]
   [1913 Webster]
   1. To make secure; to give assurance against harm; to
      guarantee safety to; to give authority or power to do, or
      forbear to do, anything by which the person authorized is
      secured, or saved harmless, from any loss or damage by his
      action.
      [1913 Webster]

            That show I first my body to warrant. --Chaucer.
      [1913 Webster]

            I'll warrant him from drowning.       --Shak.
      [1913 Webster]

            In a place
            Less warranted than this, or less secure,
            I can not be.                         --Milton.
      [1913 Webster]

   2. To support by authority or proof; to justify; to maintain;
      to sanction; as, reason warrants it.
      [1913 Webster]

            True fortitude is seen in great exploits,
            That justice warrants, and that wisdom guides.
                                                  --Addison.
      [1913 Webster]

            How little while it is since he went forth out of
            his study, -- chewing a Hebrew text of Scripture in
            his mouth, I warrant.                 --Hawthorne.
      [1913 Webster]

   3. To give a warrant or warranty to; to assure as if by
      giving a warrant to.
      [1913 Webster]

            [My neck is] as smooth as silk, I warrant ye. --L'
                                                  Estrange.
      [1913 Webster]

   4. (Law)
      (a) To secure to, as a grantee, an estate granted; to
          assure.
      (b) To secure to, as a purchaser of goods, the title to
          the same; to indemnify against loss.
      (c) To secure to, as a purchaser, the quality or quantity
          of the goods sold, as represented. See Warranty, n.,
          2.
      (d) To assure, as a thing sold, to the purchaser; that is,
          to engage that the thing is what it appears, or is
          represented, to be, which implies a covenant to make
          good any defect or loss incurred by it.
          [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

122 Moby Thesaurus words for "warranted":
   accepted, acknowledged, admitted, affianced, affirmed, alleged,
   allowed, announced, approved, ascertained, asserted, asseverated,
   assured, attested, authenticated, authorized, averred, avouched,
   avowed, balanced, betrothed, bound, certain, certified, chartered,
   committed, compromised, conceded, confessed, confirmed, contracted,
   countersigned, covered, decided, declared, defensible, deposed,
   deserved, determinate, determined, due, earned, empowered,
   endorsed, enfranchised, engaged, ensured, entitled, enunciated,
   equitable, established, even, evenhanded, fair, fair and square,
   fit, fixed, franchised, good, granted, guaranteed, in the bag,
   insured, intended, just, justifiable, justified, lawful, legal,
   level, licensed, made sure, manifestoed, meet, meet and right,
   merited, nailed down, notarized, obligated, on ice, open-and-shut,
   patented, pledged, plighted, predicated, privileged, professed,
   promised, pronounced, proper, proved, qualified, ratified,
   received, recognized, right, right and proper, rightful,
   sanctioned, sealed, secure, secured, set, settled, signed, square,
   stamped, stated, sure, sworn, sworn and affirmed, sworn to, tested,
   tried, underwritten, validated, vouched, vouched for, vowed,
   warrantable, well-earned, worthy