The Collaborative International Dictionary of English v.0.48:

Yumas \Yu"mas\, n. pl.; sing. Yuma. (Ethnol.)
   A tribe of Indians native of Arizona and the adjacent parts
   of Mexico and California. They are agricultural, and
   cultivate corn, wheat, barley, melons, etc.
   [1913 Webster]

   Note: The a wider sense, the term sometimes includes the
         Mohaves and other allied tribes.
         [1913 Webster]