Source : Webster's Revised Unabridged Dictionary (1913)

Unburden \Un*bur"den\, v. t. [1st pref. un- + burden.]
   1. To relieve from a burden.

   2. To throw off, as a burden; to unload.

Source : WordNet®

unburden
     v 1: free or relieve (someone) of a burden
     2: take the burden off; remove the burden from; "unburden the
        donkey" [syn: {disburden}] [ant: {burden}]