The Collaborative International Dictionary of English v.0.48:

Ranchero \Ran*che"ro\ (r[a^]n*ch[=a]"r[-o]), n.; pl. Rancheros
   (r[a^]n*ch[=a]"r[=o]z). [Sp.] [Mexico & Western U. S.]
   1. A herdsman; a peasant employed on a ranch or rancho.
      [1913 Webster]

   2. The owner and occupant of a ranch or rancho.
      [1913 Webster]