Hitter \Hit"ter\, n.
   1. One who hits or strikes; as, a hard hitter.
      [1913 Webster]

   2. (Baseball) The batter; as, there are two strikes on the
      hitter.
      [PJC]

   {heavy hitter}

   1. A baseball player who gets many extra-base hits.

   2. A person who is very important or is very effective at his
      profession.
      [PJC]
Source: The Collaborative International Dictionary of English

hitter
     n 1: (baseball) a ballplayer who is batting [syn: {batter}, {slugger},
           {batsman}]
     2: someone who hits; "a hard hitter"; "a fine striker of the
        ball"; "blacksmiths are good hitters" [syn: {striker}]
Source: WordNet® 2.0