an electric railway operating below the surface of the ground (usually in a city); "in Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'"
地下を走る電車(通常都市で)
tube
provide with a tube or insert a tube into
チューブを供給するか、チューブを挿入する
tube
convey in a tube; "inside Paris, they used to tube mail"
管で運ぶ
tube
ride or float on an inflated tube; "We tubed down the river on a hot summer day"