Source : Webster's Revised Unabridged Dictionary (1913)

Omahas \O"ma*has"\, n. pl.; sing. {Omaha}. (Ethnol.)
   A tribe of Indians who inhabited the south side of the
   Missouri River. They are now partly civilized and occupy a
   reservation in Nebraska.

Source : WordNet®

Omaha
     n 1: a member of the Siouan people formerly living in the
          Missouri river valley in northeastern Nebraska [syn: {Maha}]
     2: largest city in Nebraska; located in eastern Nebraska on the
        Missouri river; a major transportation center of the
        Midwest
     3: the Dhegiha dialect spoken by the Omaha people
     4: thoroughbred that won the triple crown in 1935