The Collaborative International Dictionary of English v.0.48:
fastball \fast"ball`\ n. (Baseball) a baseball thrown with maximum velocity. Syn: heater, smoke, hummer, bullet. [WordNet 1.5]WordNet (r) 3.0 (2006):
fastball n 1: (baseball) a pitch thrown with maximum velocity; "he swung late on the fastball"; "he showed batters nothing but smoke" [syn: fastball, heater, smoke, hummer, bullet]