The Collaborative International Dictionary of English v.0.48:
Llano \Lla"no\, n.; pl. Llanos. [Sp., plain even, level. See Plain.] An extensive plain with or without vegetation. [Spanish America] [1913 Webster]WordNet (r) 3.0 (2006):
llano n 1: an extensive grassy and nearly treeless plain (especially in Latin America)