The noun bullet has 3 senses (first 1 from tagged texts)
1. (35) bullet, slug -- (a projectile that is fired from a gun)
2. bullet train, bullet -- (a high-speed passenger train)
3. fastball, heater, smoke, hummer, bullet -- ((baseball) a pitch thrown with maximum velocity; "he swung late on the fastball"; "he showed batters nothing but smoke")