Underground car井下汽车undergroundadj.地下的；秘密的adv.在地下；秘密地n.地下；地铁；地道；秘密活动underground water pollution地下水污染underground railway traffic地下轨道交通underground nuclear weapons地下核武器underground heated pipeline埋地热油管道underground shopping center地下商业街underground mining cavities地下采空区underground coal mine staff煤矿井下人员Underground mud-rock flow井下泥石流underground explosion waves地下爆炸波underground railway culture地铁文化