Source : Webster's Revised Unabridged Dictionary (1913)

Plateau \Pla*teau"\, n.; pl. F. {Plateaux} (F. ?; E. ?), E.
   {Plateaus}. [F., fr. OF. platel, properly a little plate. See
   {Plate}.]
   1. A flat surface; especially, a broad, level, elevated area
      of land; a table-land.

   2. An ornamental dish for the table; a tray or salver.

Source : WordNet®

plateau
     n : a relatively flat highland [syn: {tableland}]
     [also: {plateaux} (pl)]