WordNet (r) 3.0 (2006):

summer stock
    n 1: theatrical productions performed by a stock company during
         the summer

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "summer stock":
   Broadway, burlesque, carnival, circus, drama,
   entertainment industry, legit, legitimate stage, off Broadway,
   off-off-Broadway, playland, repertory drama, show biz,
   show business, stage world, stagedom, stageland, stock, strawhat,
   strawhat circuit, the boards, the footlights, the scenes,
   the stage, the theater, theater world, theatromania, theatrophobia,
   variety, vaudeville