The Collaborative International Dictionary of English v.0.48:

Fielder \Field"er\, n. (Ball Playing)
   A ball payer who stands out in the field to catch or stop
   balls.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fielder
    n 1: a member of the baseball team that is in the field instead
         of at bat
    2: a member of the cricket team that is fielding rather than
       batting [syn: fielder, fieldsman]