The Collaborative International Dictionary of English v.0.48:

Disburden \Dis*bur"den\, v. t. [See Burden, v. t.] [Cf.
   Disburthen.]
   To rid of a burden; to free from a load borne or from
   something oppressive; to unload; to disencumber; to relieve.
   [1913 Webster]

         He did it to disburden a conscience.     --Feltham.
   [1913 Webster]

         My mediations . . . will, I hope, be more calm, being
         thus disburdened.                        --Hammond.

   Syn: To unload; unburden; discharge; free.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Disburden \Dis*bur"den\, v. i.
   To relieve one's self of a burden; to ease the mind.
   --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disburden
    v 1: take the burden off; remove the burden from; "unburden the
         donkey" [syn: unburden, disburden] [ant: burden,
         burthen, weight, weight down]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "disburden":
   abridge, alleviate, be light, bereave, bleed, break bulk, clear,
   curtail, cut off, deprive, deprive of, discharge, disembarrass,
   disembroil, disencumber, disengage, disentangle, disentitle,
   disinvolve, divest, drain, dump, ease, ease one of, extricate,
   free, free up, have little weight, kick the beam, liberate,
   lighten, lighten one of, make light, make lighter, milk, mine,
   off-load, reduce weight, relieve, set at ease, take away from,
   take from, tap, unballast, unburden, unclutter, unfreight, unlade,
   unload, unpack, unscramble, unship, unsnarl, weigh lightly