A spitball is a small piece of paper that a child chews or wets, rolls into a hard little ball, and then spits through a straw or flicks at a classmate. It belongs to the world of the school classroom, especially the American classroom, and it usually comes with the picture of a bored boy at the back and a teacher facing the blackboard. It is mainly American English; British children did much the same thing but rarely gave it this name. Two other uses are worth knowing. In baseball, a spitball is an illegal pitch where the pitcher puts spit or something slippery on the ball to make it move strangely in the air — banned for a hundred years now, but pitchers are still accused of it. And there is a very common verb, especially in offices: to spitball means to throw out rough ideas quickly without worrying whether they are good — 'let's spitball a few names for the product'. That office sense is now probably the one you will meet most often as an adult, and it is friendly and informal, never rude.

紙團（學生嚼濕後彈或吹向同學的小紙球，多為美式用法）；棒球裡的「口水球」（違規投法）；當動詞時是「隨口丟點子、腦力激盪」。