The Collaborative International Dictionary of English v.0.48:

Pampas \Pam"pas\, n. pl. [Sp., fr. Peruv. pampa a field, plain.]
   Vast grass-covered plains in the central and southern part of
   the Argentine Republic in South America. The term is
   sometimes used in a wider sense for the plains east of the
   Andes extending from Bolivia to Southern Patagonia.
   [1913 Webster]

   Pampas cat (Zool.), a South American wild cat (Felis
      pajeros). It has oblique transverse bands of yellow or
      brown. It is about three and a half feet long. Called also
      straw cat.

   Pampas deer (Zool.), a small, reddish-brown, South American
      deer (Cervus campestris syn. Blastocerus campestris).


   Pampas grass (Bot.), a very tall ornamental grass
      (Gynerium argenteum) with a silvery-white silky panicle.
      It is a native of the pampas of South America.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pampas grass
    n 1: tall perennial grass of pampas of South America having
         silvery plumes and growing in large dense clumps [syn:
         pampas grass, Cortaderia selloana]