The Collaborative International Dictionary of English v.0.48:

Skittle \Skit"tle\, a.
   Pertaining to the game of skittles.
   [1913 Webster]

   Skittle alley, an alley or court in which the game of
      skittles is played.

   Skittle ball, a disk or flattish ball of wood for throwing
      at the pins in the game of skittles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

skittle ball
    n 1: ball used to knock down ninepins [syn: ninepin ball,
         skittle ball]