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