WordNet (r) 3.0 (2006):

Sunbelt
    n 1: states in the south and southwest that have a warm climate
         and tend to be politically conservative

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "Sunbelt":
   Dixie, Dixieland, Down East, East, East Coast, Middle Atlantic,
   Middle West, New England, North, North Central region, Northeast,
   Northwest, Pacific Northwest, South, Southeast, Southwest, West,
   West Coast, Yankeeland, eastland, northland, the Coast, westland,
   wild West