What is three-cushion billiards?
three-cushion billiards meaning billiard game played on a table with three balls and no pockets. To score a point, the cue ball must contact three rails before contacting the second object ball. The first object ball can be contacted by the cue ball at any time during the shot.
reference: billiards.colostate.edu: Glossary of Pool and Billiards Terms and Phrases