The Collaborative International Dictionary of English v.0.48:

Disencumber \Dis`en*cum"ber\, v. t. [imp. & p. p.
   Disencumbered; p. pr. & vb. n. Disencumbering.] [Pref.
   dis- + encumber: cf. F. d['e]sencombrer.]
   To free from encumbrance, or from anything which clogs,
   impedes, or obstructs; to disburden. --Owen.
   [1913 Webster]

         I have disencumbered myself from rhyme.  --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disencumber
    v 1: release from entanglement of difficulty; "I cannot
         extricate myself from this task" [syn: extricate,
         untangle, disentangle, disencumber]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "disencumber":
   alleviate, be light, clear, disburden, disembarrass, disembroil,
   disengage, disentangle, disinvolve, ease, extricate, free, free up,
   have little weight, kick the beam, liberate, lighten, make light,
   make lighter, off-load, reduce weight, relieve, set at ease,
   unballast, unburden, unclutter, unfreight, unlade, unload,
   unscramble, unsnarl, untangle, untie, untwine, weigh lightly