third class noun
Learner's definition of THIRD CLASS
1 [noncount]
a : the level of service on a train, ship, etc., that is the cheapest(火车、轮船等的)三等座,三等舱 b : a class of mail in the U.S. that includes advertisements第三类邮件(在美国用于邮寄广告)
2
[singular] British : an undergraduate degree of the lowest level given by a British university(英国大学本科的)三等成绩学位