The Collaborative International Dictionary of English v.0.48:

Bullet \Bul"let\, n. [F. boulet, dim. of boule ball. See Bull
   an edict, and cf. Boulet.]
   1. A small ball.
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   2. A missile, usually of lead, and round or elongated in
      form, to be discharged from a rifle, musket, pistol, or
      other small firearm.
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   3. A cannon ball. [Obs.]
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            A ship before Greenwich . . . shot off her ordnance,
            one piece being charged with a bullet of stone.
                                                  --Stow.
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   4. The fetlock of a horse.

   Note: [See Illust. under Horse.]
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   Bullet tree. See Bully tree.

   Bullet wood, the wood of the bullet tree.
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WordNet (r) 3.0 (2006):

bullet
    n 1: a projectile that is fired from a gun [syn: bullet,
         slug]
    2: a high-speed passenger train [syn: bullet train, bullet]
    3: (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]