1.Definition: (anatomy) any hollow cylindrical body structure

Category: General

2.Definition: a hollow cylindrical shape

Related Noun(s):pipe

Category: General

3.Definition: 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'"

Related Noun(s):metro, subway, underground

Category: Objects

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

Related Noun(s):tubing

Category: Objects

5.Definition: electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

Category: Objects