The Collaborative International Dictionary of English v.0.48:

Unsheathe \Un*sheathe"\, v. t. [1st pref. un- + sheath.]
   To deprive of a sheath; to draw from the sheath or scabbard,
   as a sword.
   [1913 Webster]

   To unsheathe the sword, to make war.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unsheathe
    v 1: draw from a sheath or scabbard; "the knight unsheathed his
         sword" [ant: sheathe]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "unsheathe":
   bare, break the seal, bring to light, clear, denudate, denude,
   deobstruct, develop, disclose, discover, dismask, divest,
   draw the veil, expose, fleece, free, impart, lay bare, lay open,
   let daylight in, let out, manifest, open, open up, patefy, pluck,
   raise the curtain, remove, reveal, shear, show, show up, strip,
   strip bare, unblock, uncase, unclench, uncloak, unclog, unclutch,
   uncork, uncover, uncurtain, undo, undrape, unfold, unfoul, unfurl,
   unkennel, unlatch, unlock, unmask, unpack, unplug, unroll,
   unscreen, unseal, unshroud, unshut, unstop, unveil, unwrap