- 1connected with the class of mail used to send advertisements, etc.
- 2(especially in the past) connected with the cheapest and least comfortable way of traveling on a train, ship, etc.
- 3(disapproving) (of people) less important than other people They are treated as third-class citizens.
adverb to travel third classSee third-class in the Oxford Advanced Learner's Dictionary
Check pronunciation: third-class