tube - noun

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)

tube - verb

• provide with a tube or insert a tube into
• convey in a tube
• ride or float on an inflated tube
• place or enclose in a tube

tube - thesaurus

metro   pipe   subway   tubing   underground