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. [1913 Webster] 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. [1913 Webster] Rack vintage, wine cleansed and drawn from the lees. --Cowell. [1913 Webster]