低下
low status; lowly; to lower (one's head)
地下
underground; subterranean; covert
底下
the location below sth; afterwards
涤瑕
to cleanse away a stain
地下核爆炸
nuclear underground burst; underground nuclear explosion
地下核试验
underground nuclear test
地下通道
underpass; subway; tunnel
人行地下通道
pedestrian underpass
大树底下好乘凉
lit. under a big tree the shade is plentiful (idiom); fig. to benefit by proximity to an influential person
排污地下主管网
underground sewage network