brush up on something
— phrasal verb with brush us/brʌʃ/verb
to improve your knowledge of something already learned but partly forgotten:
You’d better brush up on your French before going to Paris.
英语词典包含110679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。