大忙

nǐ bāng le wǒ yī gè dà máng wǒ fēi cháng gǎn xiè nǐ

你帮了我一个大忙，我非常感谢你。

You have been a great help, and I'm very grateful to you.

dà máng shí kè

大忙时刻

busy moment

dà máng shí jié

大忙时节

rush season

xiào zhǎng kě shì gè dà máng rén

校长可是个大忙人。

The principal is a very busy person.