subway; metro; underground (railway)
underground space; subterranean space; subterranea
underground shopping center; underground shopping centre
groundwater; underground water
second basement level; subbasement
to go underground; to go into hiding
semibasement; semi-basement
member of a non-famous boy band or girl group; (lit.) underground idol
underground organization; underground organisation
basement of a department store (where foodstuffs are usually sold)
subway; metro; underground railway
second basement level; subbasement
crypt; underground chapel
basement floor; underground floor
underground activity; underground activities; underground movement
deep subterranean area; deep underground
underground shopping arcade connected to a station
underground lake; subterranean lake
underground publication; underground publishing; samizdat
underground resistance (in wartime)
clandestine bank; underground bank
underground economy; black economy
burying; underground installation (cables, etc.)
underground wire or cable
underground train station
underground activities; secret maneuvering
water table; groundwater level
first basement floor; first floor underground; lower ground floor
London Underground mosquito (Culex pipiens f. molestus)
sunken hearth; sunken fireplace