surface mail
noun [ U ] uk/ˈsɜː.fɪs ˌmeɪl/ us/ˈsɝː.fɪs ˌmeɪl/
平邮，平信，普通邮件
a way of sending letters, parcels, etc. by road, sea, or train and not by aircraft, or things sent in this way
I sent the parcel by surface mail. 我用平邮把包裹寄了出去。
英汉双解词典收录81607条英汉双解翻译词条，基本涵盖了全部常用单词的读音、翻译及用法，是英语学习的有利工具。