老师掸掉黑板擦上的粉笔灰.

The teacher beat chalk dust from erasers.

那班顽皮学生闹著玩儿,捏碎不少粉笔,过后, 教室地板上撒满了粉笔灰.

After the horseplay by the wicked students, the classroom floor was strewn with crumbled chalk dust.

实际上，光束会穿过彼此，你自己也可以做个实验，用两支激光笔和粉笔灰就行了。

The beams of light pass right through each other as you can check for yourself with two laser pointers and some chalk dust.

我外套上弄上一些粉笔灰了。

I've got some chalk on my coat.

她象从前吸着你巧妙修辞的粉笔灰。

Inhaled the chalk-dust of your rhetoric.