The Collaborative International Dictionary of English v.0.48:

Lacrosse \La*crosse"\, n. [F. la crosse, lit., the crosier,
   hooked stick. Cf. Crosier.]
   A game of ball, originating among the North American Indians,
   now the popular field sport of Canada, and played also in
   England and the United States. Each player carries a
   long-handled racket, called a "crosse". The ball is not
   handled but caught with the crosse and carried on it, or
   tossed from it, the object being to carry it or throw it
   through one of the goals placed at opposite ends of the
   field.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lacrosse
    n 1: a game invented by American Indians; now played by two
         teams who use long-handled rackets to catch and carry and
         throw the ball toward the opponents' goal