The Collaborative International Dictionary of English v.0.48:

Handball \Hand"ball`\ (h[a^]nd"b[add]l`), n.
   1. A small ball, usually made of rubber, thrown or struck
      with the hand in various games.
      [Webster 1913 Suppl.]

   2. A game played with such a ball, as by players striking it
      to and fro between them with the hands, or, when played in
      a walled court or against a single wall, striking it in
      turns against a wall, until one side or the other fails to
      return the ball.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

handball
    n 1: a small rubber ball used in playing the game of handball
    2: a game played in a walled court or against a single wall by
       two or four players who strike a rubber ball with their hands