Cannonball

The fastest type of service - hit flat and so severely that it booms into an opponent's box, often for an ace. The term seems to have first been coined by sportswriters with reference to Bill Tilden's tremendous serve. During the years in the 1920's when he dominated the tennis world, his serve was credited with traveling 163.6 m.p.h. When facing a cannonball serve of that order, ducking would seem the better part of valor.