Source : WordNet®

jacks
     n 1: plaything consisting of small 6-pointed metal pieces that
          are used (along with a ball) to play the game of jacks
          [syn: {jackstones}]
     2: a game in which jackstones are thrown and picked up in
        various groups between bounces of a small rubber ball
        [syn: {jackstones}, {knucklebones}]