The Collaborative International Dictionary of English v.0.48:

spitball \spit"ball`\, spit ball \spit" ball`\, n.
   1. Paper chewed, and rolled into a ball, to be thrown as a
      missile; -- a childish prank.
      [1913 Webster]

   2. (Baseball) A pitched ball in throwing which the pitcher
      grips the ball between two, or three, fingers on one side
      (which is made slippery, as by saliva) and the thumb on
      the other side, and delivers it so that it slips off the
      fingers with the least possible friction; -- also called
      spitter. When pitched directly overhand a spit ball
      darts downward, when pitched with the arm extended
      sidewise it darts down and out. The use of such a pitch is
      against the rules of professional baseball. [Cant] --
      Spit baller.
      [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

Spitter \Spit"ter\, n. [See Spit to eject from the mouth.]
   One who ejects saliva from the mouth.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spitter \Spit"ter\, n. [See Spit an iron prong.]
   1. One who puts meat on a spit.
      [1913 Webster]

   2. (Zool.) A young deer whose antlers begin to shoot or
      become sharp; a brocket, or pricket.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spitter
    n 1: a person who spits (ejects saliva or phlegm from the mouth)
         [syn: spitter, expectorator]
    2: an illegal pitch in which a foreign substance (spit or
       Vaseline) is applied to the ball by the pitcher before he
       throws it [syn: spitball, spitter]