The Collaborative International Dictionary of English v.0.48:

Catcher \Catch"er\, n.
   1. One who, or that which, catches.
      [1913 Webster]

   2. (Baseball) The player who stands behind the batsman to
      catch the ball.
      [1913 Webster]

WordNet (r) 3.0 (2006):

catcher
    n 1: (baseball) the person who plays the position of catcher
         [syn: catcher, backstop]
    2: the position on a baseball team of the player who is
       stationed behind home plate and who catches the balls that
       the pitcher throws; "a catcher needs a lot of protective
       equipment"; "a catcher plays behind the plate"