The Collaborative International Dictionary of English v.0.48:

Polka \Pol"ka\, n. [Pol. Polka a Polish woman: cf. F. & G.
   polka.]
   1. A dance of Polish origin, but now common everywhere. It is
      performed by two persons in common time.
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   2. (Mus.) A lively Bohemian or Polish dance tune in 2-4
      measure, with the third quaver accented.
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   Polka jacket, a kind of knit jacket worn by women.
      [1913 Webster]