TUBE

noun

1. Anything that is hollow and cylindrical in shape.
2. An approximately cylindrical container, usually with a crimped end and a screw top, used to contain and dispense semiliquid substances.
3. (often capitalized as Tube) The London Underground railway system, originally referred to the lower level lines that ran in tubular tunnels as opposed to the higher ones which ran in rectangular section tunnels. (Often the tube.)

verb

1. To supply with, or enclose in, a tube.
2. To ride an inner tube.
3. To intubate.