[third class] n (1844) 1: the third and usu. next below second class in a classification
2: the least expensive class of accommodations (as on a passenger ship) 3 a: a class of U.S. mail comprising printed matter exclusive of regularly issued periodicals and merchandise less than 16 ounces (454 grams) in weight that is not sealed against inspection b: a similar class of Canadian mail with different weight limits