tube

conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases

electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

a hollow cylindrical shape

(anatomy) any hollow cylindrical body structure

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'"

provide with a tube or insert a tube into

convey in a tube; "inside Paris, they used to tube mail"

ride or float on an inflated tube; "We tubed down the river on a hot summer day"

place or enclose in a tube