Synonyms for tube

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

• tubing

electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope (noun)

a hollow cylindrical shape (noun)

• pipe

(anatomy) any hollow cylindrical body structure (noun)

an electric railway operating below the surface of the ground (usually in a city) (noun)

• metro
• underground
• subway