The Collaborative International Dictionary of English v.0.48:

Javelin \Jave"lin\, n. [F. javeline; akin to Sp. jabalina, It.
   giavelina, and F. javelot, OF. gavlot. Cf. Gavelock.]
   1. A sort of light spear, to be thrown or cast by the hand;
      anciently, a weapon of war used by horsemen and foot
      soldiers; now used chiefly in hunting the wild boar and
      other fierce game.
      [1913 Webster]

            Flies the javelin swifter to its mark,
            Launched by the vigor of a Roman arm? --Addison.
      [1913 Webster]

   2. (Sport) A wooden shaft resembling a spear, thrown by
      contestants in a contest called the javelin throw; the one
      throwing the javelin furthest wins the contest. The
      javelin throw is one of the field events of the modern
      Olympic Games.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Javelin \Jave"lin\, v. t.
   To pierce with a javelin. [R.] --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

javelin
    n 1: an athletic competition in which a javelin is thrown as far
         as possible
    2: a spear thrown as a weapon or in competitive field events