tube
n. countablen. a long, hollow object shaped like a pipe that holds or moves liquids and gases. It can also refer to the underground train system in London.
n. a hollow cylinder used for the conveyance or containment of fluids or gases. When used with the definite article, it refers specifically to the London Underground railway system.
The artist squeezes blue paint from the tube.
The doctor inserted a thin tube into the patient's arm to provide necessary fluids.
Engineers designed a reinforced steel tube to withstand the immense pressure of the deep-sea environment while transporting natural gas to the surface.
From Middle French tube, from Latin tubus (“tube, pipe”), related to tuba (“long trumpet; war-trumpet”), of obscure ultimate origin, but possibly connected to tībia (“shinbone, reed-pipe”); see there. Doublet of tubus.
Often used with the definite article ('the Tube') when referring to the London subway system.