The Collaborative International Dictionary of English v.0.48:

malt whiskey \malt whiskey\, malt whisky \malt whisky\n.
   A whiskey distilled in Scotland (esp. whiskey made from
   malted barley in a pot still); Scotch whisky.

   Syn: Scotch, Scotch-whiskey, Scotch whisky.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

malt whiskey
    n 1: whiskey distilled in Scotland; especially whiskey made from
         malted barley in a pot still [syn: Scotch, Scotch
         whiskey, Scotch whisky, malt whiskey, malt whisky,
         Scotch malt whiskey, Scotch malt whisky]