1to grasp (often fig.)
2to control
3to seize (initiative, opportunity, destiny)
4to master
5to know well
6to understand sth well and know how to use it
7fluency
Examples
zhè这gè个kè chéng课程néng能bāng zhù帮助nǐ你zhǎng wò掌握zhèng què正确fā yīn发音。
这个课程能帮助你掌握正确发音。
This course will help you master correct pronunciation.
短时间内掌握英语是很重要的。
It is very important to master English in short time.
掌握一门外语很难。
Mastering a foreign language is difficult.