underground

1. ADV Something that is underground is below the surface of the ground. 在地下[ADV after v]

Solid low-level waste will be disposed of deep underground. 低放射性固躰廢物將被棄置在地下深処。

2. ADJ Underground is also an adjective. 地下的[ADJ n]

...an underground parking garage for 2,100 vehicles. …一座能停放2100輛車的地下停車庫。

3. N-SING Theunderground in a city is the railway system in which electric trains travel below the ground in tunnels. 地鉄[英國英語] ['the' N, also 'by' N]

I don't travel on the underground late at night. 我深夜不坐地鉄。

4. ADJ Underground groups and activities are secret because their purpose is to oppose the government and they are illegal. 秘密的; 地下的[ADJ n]

...the underground Kashmir Liberation Front. 秘密的尅什米爾解放陣線。

5. ADV If you go underground, you hide from the authorities or the police because your political ideas or activities are illegal. 秘密地; 在地下[ADV after v]

After the violent clashes of 1981 they either went underground or left the country. 1981年的暴力沖突之後，他們要麼轉入地下了，要麼離開了這個國家。