unbuckle

from WordNet (r) 3.0 (2006)

unbuckle
    v 1: undo the buckle of; "Unbuckle your seat belt" [ant:
         {buckle}, {clasp}]

from The Collaborative International Dictionary of English v.0.48

Unbuckle \Un*buc"kle\, v. t. [1st pref. un- + buckle.]
   To loose the buckles of; to unfasten; as, to unbuckle a shoe.
   "Unbuckle anon thy purse." --Chaucer.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

45 Moby Thesaurus words for "unbuckle":
      cast off, detach, disengage, doff, free, liberate, loose, loosen,
      release, remove, take off, unbar, unbind, unbolt, unbridle,
      unbutton, uncage, unchain, unclasp, undo, unfasten, unfetter,
      ungag, unglue, unhandcuff, unhobble, unlace, unlash, unlatch,
      unleash, unlock, unloose, unloosen, unmanacle, unmuzzle, unpen,
      unpinion, unshackle, unstick, unstrap, untether, untie, untruss,
      unyoke, weigh anchor