The Collaborative International Dictionary of English v.0.48:

Muscadet \Muscadet\ n.
   1. A white grape grown esp. in the Loire Valley in France.
      [WordNet 1.5]

   2. A dry white wine from the Loire Valley in France.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

Muscadet
    n 1: white grape grown especially in the valley the Loire in
         France
    2: dry white wine from the Loire valley in France