The Collaborative International Dictionary of English v.0.48:

Rack \Rack\, v. t. [Cf. OF. vin raqu['e] wine squeezed from the
   dregs of the grapes.]
   To draw off from the lees or sediment, as wine.
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         It is in common practice to draw wine or beer from the
         lees (which we call racking), whereby it will clarify
         much the sooner.                         --Bacon.
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   Rack vintage, wine cleansed and drawn from the lees.
      --Cowell.
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