The Collaborative International Dictionary of English v.0.48:

Unlade \Un*lade"\ v. t. [1st un- + lade.]
   1. To take the load from; to take out the cargo of; as, to
      unlade a ship or a wagon.
      [1913 Webster]

            The venturous merchant . . .
            Shall here unlade him and depart no more. --Dryden.
      [1913 Webster]

   2. To unload; to remove, or to have removed, as a load or a
      burden; to discharge.
      [1913 Webster]

            There the ship was to unlade her burden. --Acts.
                                                  xxi. 3.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unlade
    v 1: take the load off (a container or vehicle); "unload the
         truck"; "offload the van" [syn: unload, unlade,
         offload]