A gumball is chewing gum made as a small, hard, round sweet, usually in a very bright colour — red, blue, green, yellow. You typically get one from a machine: you put in a coin, turn the handle, and a ball drops into the little door. You suck or chew the sugary shell; then gum is left in your mouth. It is a strongly American word, but the machines are known in many countries. Though actually, in the United States people also nicknamed the round coloured light on an old police car a gumball, because it looked like one. That is a joke-name for a light, not a second kind of sweet.