Spitball (noun)

1. A ball of paper, often moistened and rolled, that is thrown by hand.
2. A small wad of paper that is thrown as a prank or for amusement.

Origin:

A ball of paper, often moistened and rolled, that is thrown by hand.

Examples:

1. The kids were throwing spitballs in class and got in trouble with the teacher.
2. He was caught throwing a spitball at the back of the teacher's head.
3. The spitball hit the window and left a wet mark.
4. He made a spitball and threw it at his friend as a joke.
5. The spitball was made with a small amount of saliva to make it stick together.