Source : Webster's Revised Unabridged Dictionary (1913)

Llano \Lla"no\, n.; pl. {Llanos}. [Sp., plain even, level. See
   {Plain}.]
   An extensive plain with or without vegetation. [Spanish
   America]

Source : WordNet®

llano
     n : an extensive grassy and nearly treeless plain (especially in
         Latin America)