The Collaborative International Dictionary of English v.0.48:

Plume \Plume\, n. [F., fr. L. pluma. Cf. Fly, v.]
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   1. A feather; esp., a soft, downy feather, or a long,
      conspicuous, or handsome feather.
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            Wings . . . of many a colored plume.  --Milton.
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   2. (Zool.) An ornamental tuft of feathers.
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   3. A feather, or group of feathers, worn as an ornament; a
      waving ornament of hair, or other material resembling
      feathers.
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            His high plume, that nodded o'er his head. --Dryden.
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   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.
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   5. (Bot.) A large and flexible panicle of inflorescence
      resembling a feather, such as is seen in certain large
      ornamental grasses.
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   Plume bird (Zool.), 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 Erianthus Ravenn[ae] from the
          Mediterranean region. The name is sometimes extended
          to the whole genus.

   Plume moth (Zool.), 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.
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WordNet (r) 3.0 (2006):

Erianthus ravennae
    n 1: grass often cultivated for its long white-ribbed leaves and
         large plumes resembling those of pampas grass [syn:
         Ravenna grass, wool grass, Erianthus ravennae]