Noun:
1: tube, tubing conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases
2: thermionic valve, thermionic tube, thermionic vacuum tube, electron tube, tube, vacuum tube electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope
3: pipe, tube a hollow cylindrical shape
4: tube-shaped structure, tube (anatomy) any hollow cylindrical body structure
5: subway system, tube, underground, subway, metro 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'"
Verb:
1: tube provide with a tube or insert a tube into
2: tube convey in a tube; "inside Paris, they used to tube mail"
3: tube ride or float on an inflated tube; "We tubed down the river on a hot summer day"
4: tube place or enclose in a tube