Source : Webster's Revised Unabridged Dictionary (1913)

Plume \Plume\, n. [F., fr. L. pluma. Cf. {Fly}, v.]
   1. A feather; esp., a soft, downy feather, or a long,
      conspicuous, or handsome feather.

            Wings . . . of many a colored plume.  --Milton.

   2. (Zo["o]l.) An ornamental tuft of feathers.

   3. A feather, or group of feathers, worn as an ornament; a
      waving ornament of hair, or other material resembling
      feathers.

            His high plume, that nodded o'er his head. --Dryden.

   4. A token of honor or prowess; that on which one prides
      himself; a prize or reward. ``Ambitious to win from me
      some plume.'' --Milton.

   5. (Bot.) A large and flexible panicle of inflorescence
      resembling a feather, such as is seen in certain large
      ornamental grasses.

   {Plume bird} (Zo["o]l.), any bird that yields ornamental
      plumes, especially the species of Epimarchus from New
      Guinea, and some of the herons and egrets, as the white
      heron of Florida ({Ardea candidissima}).

   {Plume grass}. (Bot)
      (a) A kind of grass ({Erianthus saccharoides}) with the
          spikelets arranged in great silky plumes, growing in
          swamps in the Southern United States.
      (b) The still finer {E. Ravenn[ae]} from the Mediterranean
          region. The name is sometimes extended to the whole
          genus.

   {Plume moth} (Zo["o]l.), any one of numerous small, slender
      moths, belonging to the family {Pterophorid[ae]}. Most of
      them have the wings deeply divided into two or more
      plumelike lobes. Some species are injurious to the
      grapevine.

   {Plume nutmeg} (Bot.), an aromatic Australian tree
      ({Atherosperma moschata}), whose numerous carpels are
      tipped with long plumose persistent styles.

Source : WordNet®

plume grass
     n : a reedlike grass of the genus Erianthus having large plumes