a.

1. 地下的，地面下的
   An underground passage leads to the building across the street.

   一条地下通道通到街对面的大楼。

2. 秘密的，不公开的
   They were suspected of underground activities.

   他们被怀疑进行地下活动。

3. （电影，戏剧等）反主流的，先锋派的

n.[C][theS]

1. 地面下层
2. （常大写）【英】地下铁
   I used to go to work by underground when I was in London.

   我在伦敦时，通常乘地铁上班。

3. （旨在反对现存政府等的）地下组织[G]
   He joined the underground to fight against the fascists.

   他参加了地下组织与法西斯作战。

4. （常大写）先锋派团体[G]

ad.

1. 在地下
   Miners work underground.

   矿工在地下工作。

2. 秘密地，不公开地
   He went underground to avoid capture.

   他转入秘密工作以免被捕。

adj.

adv.

1. beneath the surface of the ground.
2. in secrecy or hiding, especially as a result of carrying out subversive political activities.
3. seeking to explore alternative forms of lifestyle or artistic expression; radical and experimental.

n.

1. (often the Underground) Brit. an underground railway, especially the one in London.
2. a group or movement organized secretly to work against an existing regime.
3. a group or movement seeking to explore alternative forms of lifestyle or artistic expression.