grind one's teeth 磨牙

　　grind 磨，碾

　　Some people grind their teeth while they are asleep.

　　有些人睡觉时磨牙齿。

　　My roommate Jack always grinds his teeth in his sleep, which is a totally disaster.

　　我室友Jack喜欢睡觉磨牙，这对我就是个灾难。

　　疯狂练习吧！