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]