The Collaborative International Dictionary of English v.0.48:

Sheathe \Sheathe\, v. t. [imp. & p. p. Sheathed; p. pr. & vb.
   n. Sheating.] [Written also sheath.]
   1. To put into a sheath, case, or scabbard; to inclose or
      cover with, or as with, a sheath or case.
      [1913 Webster]

            The leopard . . . keeps the claws of his fore feet
            turned up from the ground, and sheathed in the skin
            of his toes.                          --Grew.
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            'T is in my breast she sheathes her dagger now.
                                                  --Dryden.
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   2. To fit or furnish, as with a sheath. --Shak.
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   3. To case or cover with something which protects, as thin
      boards, sheets of metal, and the like; as, to sheathe a
      ship with copper.
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   4. To obtund or blunt, as acrimonious substances, or sharp
      particles. [R.] --Arbuthnot.
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   To sheathe the sword, to make peace.
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The Collaborative International Dictionary of English v.0.48:

Sheathed \Sheathed\, a.
   1. Povided with, or inclosed in, sheath.
      [1913 Webster]

   2. (Bot.) Invested by a sheath, or cylindrical membranaceous
      tube, which is the base of the leaf, as the stalk or culm
      in grasses; vaginate.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sheathed
    adj 1: enclosed in a protective covering; sometimes used in
           combination; "his sheathed sword"; "the cat's sheathed
           claws"; "a ship's bottom sheathed in copper"; "copper-
           sheathed" [ant: bare, unsheathed]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "sheathed":
   armored, cased, ceiled, cloaked, clouded, coated, coped, covered,
   covert, cowled, curtained, eclipsed, encapsulated, encapsuled,
   encased, enveloped, enwrapped, filmed, floored, hooded, housed,
   loricate, loricated, mantled, masked, muffled, obscured, occulted,
   packaged, paved, roofed-in, screened, scummed, shelled, shielded,
   shrouded, swathed, tented, under cover, veiled, walled, walled-in,
   wrapped