:the best or highest group or class头等;最高级: such as
a :the best of usually three kinds of service you can have when you travel头等服务
flying in first class坐飞机的头等舱b
b :a class of mail in the U.S. that includes letters and postcards第一类邮件(在美国用于邮寄信件和明信片)
c :a class of mail in the U.K. that includes letters and packages which are delivered sooner than ordinary second-class mail but cost more to send第一类邮件(在英国指投递更快但邮资更高的邮件,通常邮寄信件和包裹)