shot clock

Noun

 * 1)  A timer measuring the length of time since the last shot.
 * 2)  A countdown of the time remaining within which the current server must serve the ball.
 * 3) * 2017 November 17 "Shot clock introduced for all Grand Slams" RTÉ, Ireland:
 * Top tennis stars will come under a 25-second shot clock in grand slam tournaments starting at the Australian Open in January.
 * 1)  A counter of the total shots on net for a team in a game; or average shots on net per unit time for a game.