Source : Webster's Revised Unabridged Dictionary (1913)

Unimproved \Un`im*proved"\, a.
   1. Not improved; not made better or wiser; not advanced in
      knowledge, manners, or excellence.

   2. Not used; not employed; especially, not used or employed
      for a valuable purpose; as, unimproved opportunities;
      unimproved blessings. --Cowper.

   3. Not tilled, cultivated, or built upon; yielding no
      revenue; as, unimproved land or soil.

Source : WordNet®

unimproved
     adj 1: not made more desirable or valuable or profitable;
            especially not made ready for use or marketing; "taxes
            on unimproved land are low"; "unimproved dirt roads"
            [ant: {improved}]
     2: (of land) not cleared of trees and brush; in the wild or
        natural state; "a farm with 50 acres of unimproved and 68
        acres of improved land"; "unimproved woodlands"