The Collaborative International Dictionary of English v.0.48:

Agitator \Ag"i*ta`tor\, n. [L.]
   1. One who agitates; one who stirs up or excites others; as,
      political reformers and agitators.
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   2. (Eng. Hist.) One of a body of men appointed by the army,
      in Cromwell's time, to look after their interests; --
      called also adjutators. --Clarendon.
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   3. An implement for shaking or mixing.
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