打埋伏

打埋伏:

Literally means:

set an ambush; hold something back for one's own purpose

Actually means:

It means setting military forces secretly on the enemy's way so as to attack at the right moment.

It figuratively means concealing a fact or problem from someone, or to withhold what should be handed in. Derogatory.

指打仗时在敌人要经过的地方秘密布置兵力，等待机会打击敌人。

比喻隐瞒事实或问题，或隐藏应该上缴的东西。具有贬义色彩。