0 a ball used in the game of billiards (= a game played by two people on a table covered in soft cloth, in which a long stick is used to hit balls against each other and into pockets around the table):
When you do physics, you study rather boring sorts of objects, like billiard balls that collide and so on.
His best-known discovery, made in the search of a substitute for the ivory used in billiard balls, was the plastic celluloid.
Like billiard balls scattered on a pool table, the stories collide and coexist.
Now you can see in the picture that I am bald as a billiard ball.
