Source : Webster's Revised Unabridged Dictionary (1913)

Dune \Dune\, n. [The same word as down: cf. D. duin. See {Down}
   a bank of sand.]
   A low hill of drifting sand usually formed on the coats, but
   often carried far inland by the prevailing winds. [Written
   also {dun}.]

         Three great rivers, the Rhine, the Meuse, and the
         Scheldt, had deposited their slime for ages among the
         dunes or sand banks heaved up by the ocean around their
         mouths.                                  --Motley.

Source : WordNet®

dune
     n : a ridge of sand created by the wind; found in deserts or
         near lakes and oceans [syn: {sand dune}]