WordNet (r) 3.0 (2006):

second class
    adv 1: by second class conveyance; "we traveled second class"
    n 1: not the highest rank in a classification
    2: not the highest quality in a classification
    3: a class of accommodations on a ship or train or plane that
       are less expensive than first class accommodations [syn:
       cabin class, second class, economy class]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "second class":
   Mickey Mouse, base, cheap, cheesy, coarse, common, declasse,
   fourth-class, hack, inferior, irregular, low-class, low-grade,
   low-quality, low-test, mean, paltry, poor, punk, second-best,
   second-rate, seedy, shabby, tacky, third-class, third-rate,
   tinny