The Collaborative International Dictionary of English v.0.48:

Raisin \Rai"sin\ (r[=a]"z'n), n. [F. raisin grape, raisin, L.
   racemus cluster of grapes or berries; cf. Gr. "ra`x, "rago`s,
   berry, grape. Cf. Raceme.]
   1. A grape, or a bunch of grapes. [Obs.] --Cotgrave.
      [1913 Webster]

   2. A grape dried in the sun or by artificial heat.
      [1913 Webster]

   Raisin tree (Bot.), the common red currant bush, whose
      fruit resembles the small raisins of Corinth called
      currants. [Eng.] --Dr. Prior.
      [1913 Webster]

WordNet (r) 3.0 (2006):

raisin
    n 1: dried grape