The Collaborative International Dictionary of English v.0.48:

Cheyennes \Chey*ennes"\, n. pl.; sing. cheyenne. (Ethnol.)
   A warlike tribe of indians, related to the blackfeet,
   formerly inhabiting the region of Wyoming, but now mostly on
   reservations in the Indian Territory. They are noted for
   their horsemanship.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Cheyenne
    n 1: the capital and largest city of Wyoming; located in the
         southeastern corner of the state [syn: Cheyenne, capital
         of Wyoming]
    2: the Algonquian language spoken by the Cheyenne
    3: a member of a North American Indian people living on the
       western plains (now living in Oklahoma and Montana)