Source : Webster's Revised Unabridged Dictionary (1913)

Blackfoot \Black"foot`\, a.
   Of or pertaining to the Blackfeet; as, a Blackfoot Indian. --
   n. A Blackfoot Indian.

Source : WordNet®

Blackfoot
     n 1: a member of a warlike group of Algonquians living in the
          northwestern plains
     2: any of the Algonquian languages spoken by the Blackfoot
        people