The Collaborative International Dictionary of English v.0.48:

gumball \gum"ball`\ (g[u^]m"b[add]l), n.
   A piece of chewing gum in the shape of a ball, usually
   covered with a colored glaze of sugar. They are often sold in
   a small, special-purpose coin-operated vending machine called
   a gumball machine.
   [PJC]