1. (

• tube ,
• tubing

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

2. (

• tube ,
• vacuum_tube ,
• thermionic_vacuum_tube ,
• thermionic_tube ,
• electron_tube ,
• thermionic_valve

) 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 ,
• tube-shaped_structure

) (anatomy) any hollow cylindrical body structure ;

5. (

• metro ,
• tube ,
• underground ,
• subway_system ,
• subway

) 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'" ;

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 ;