The Collaborative International Dictionary of English v.0.48:

Beater \Beat"er\ (b[=e]t"[~e]r), n.
   1. One who, or that which, beats.
      [1913 Webster]

   2. A person who beats up game for the hunters. --Black.
      [1913 Webster]

WordNet (r) 3.0 (2006):

beater
    n 1: a worker who rouses wild game from under cover for a hunter
    2: an implement for beating

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "beater":
   Nimrod, agitator, big game hunter, blender, cement mixer, churn,
   courser, crucible, eggbeater, emulsifier, hunter, huntress,
   huntsman, jacker, jacklighter, jiggler, melting pot, mixer, paddle,
   shaker, shikari, sportsman, sportswoman, stalker, trapper,
   vibrator, whisk, white hunter