Squash
Squash is a racket sport played by two (singles) or four players (doubles) in a four-walled court with a small, hollow rubber ball. The players must alternate in striking the ball with their racket and hit the ball onto the playable surfaces of the four walls of the court.
The game was formerly called squash rackets, a reference to the "squashable" soft ball used in the game (compared with the harder ball used in its sister game rackets).
The standard ball for professional competitions is the double yellow according to the World Squash Federation.