The Collaborative International Dictionary of English v.0.48:

Bolas \Bo"las\, n. sing. & pl. [Sp.]
   A kind of missile weapon consisting of one, two, or more
   balls of stone, iron, or other material, attached to the ends
   of a leather cord; -- used by the Gauchos of South America,
   and others, for hurling at and entangling an animal.
   [1913 Webster]