(especially in the past) connected with the cheapest and least comfortable way of travelling on a train, ship, etc.三等的（尤指旧时火车座位、轮船舱位等）Topics Transport by waterb1
(in the US) connected with the class of mail used to send advertisements, etc.第三类的（美国邮件等级）
[only before noun]used to describe the lowest standard of degree given by a British university第三等的（英国大学学位）Topics Educationc2
(disapproving)(of people人)less important than other people第三等的；卑微的
They are treated as third-class citizens.他们被当成三等公民对待。🔊🔊