From WordNet (r) 3.0 (2006):
tube
n 1: conduit consisting of a long hollow object (usually
cylindrical) used to hold and conduct objects or liquids or
gases [syn: tube, tubing]
2: electronic device consisting of a system of electrodes
arranged in an evacuated glass or metal envelope [syn:
tube, vacuum tube, thermionic vacuum tube, thermionic
tube, electron tube, thermionic valve]
3: a hollow cylindrical shape [syn: pipe, tube]
4: (anatomy) any hollow cylindrical body structure [syn: tube,
tube-shaped structure]
5: 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'" [syn: metro, tube, underground, subway
system, subway]
v 1: provide with a tube or insert a tube into
2: convey in a tube; "inside Paris, they used to tube mail"
3: ride or float on an inflated tube; "We tubed down the river
on a hot summer day"
4: place or enclose in a tube