Chewing gum sold as a ball usually coated with colored hard sugar. / (slang) A silly, laughable person. / (US, slang) The flashing lights on top of a police car.

plural of gumball

A coin-operated machine that dispenses gumballs. / (slang) The flashing light on top of a police car. / (slang, by extension) A police car.

plural of gumball machine