underground

n. 地下,地铁,地道,秘密活动
a. 地下的,秘密的
ad. 在地下,秘密地

There is an underground car park near the supermarket.

这个超市附近有一个地下停车场。

The spy never told his family about his underground activities.

这位间谍从未把他的秘密活动告诉家里人。