He was vain about his looks, spending hours in the gym.
They made a vain attempt to protect the town from attack.
He underwent a knee operation in the vain hope of getting into the team.
英语词典包含67175条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。