The Collaborative International Dictionary of English v.0.48:

Drummer \Drum"mer\, n.
   1. One whose office is to best the drum, as in military
      exercises and marching.
      [1913 Webster]

   2. One who solicits custom; a commercial traveler. [Colloq.
      U.S.] --Bartlett.
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   3. (Zool.) A fish that makes a sound when caught; as:
      (a) The squeteague.
      (b) A California sculpin.
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   4. (Zool.) A large West Indian cockroach (Blatta gigantea)
      which drums on woodwork, as a sexual call.
      [1913 Webster]