line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight | conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases |
a line of track providing a runway for wheels | an electric railway operating below the surface of the ground (usually in a city) |
| electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope |
| (anatomy) any hollow cylindrical body structure |
| a hollow cylindrical shape |