tube

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A hollow cylinder, especially one that conveys a fluid or functions as a passage.
• noun An organic structure having the shape or function of a tube; a duct.
• noun A small flexible cylindrical container sealed at one end and having a screw cap at the other, for pigments, toothpaste, or other pastelike substances.
• noun Music The cylindrical part of a wind instrument.
• noun An electron tube.
• noun A vacuum tube.
• noun Botany The lower, cylindrical part of a gamopetalous corolla or a gamosepalous calyx.
• noun A tunnel.
• noun An underground railroad system, especially the one in London, England.
• noun The elongated space inside a wave when it is breaking.
• noun An inner tube.
• noun An inflatable tube or cushion made of rubber or plastic and used for recreational riding, as behind a motor boat or down a snow-covered slope.
• noun Television.
• noun A television set.
• noun Informal The fallopian tubes.
• intransitive verb To provide with a tube; insert a tube in.
• intransitive verb To place in or enclose in a tube.
• intransitive verb To ride or float on an inflated tube for recreation.
• idiom (tubes/tube) Into a state of failure or ruin.

from The Century Dictionary.

• To furnish with a tube or tubes.
• To receive or inclose in a tube.
• noun A city subway in the form of a tunnel.
• A pipe or hollow cylinder, especially when of small size and used as a conduit for liquids, or for containing liquids, as in some forms of scientific apparatus.
• Specifically, the main body of a musical instrument of either the wood wind or the brass wind group. The bore of such instruments is usually conical, but sometimes cylindrical.
• In anatomy and zoology, a hollow tubular organ; a pipe, canal, or duct conveying fluid or gas; especially, a pipe which seems to be empty—that is, conveys air: as, the bronchial tubes; the Eustachian tube.
• In botany, any hollow elongated body or part of an organ: applied especially to a gamopet-alous corolla or gamosepalous calyx, also to a united circle of stamens (see cut 9 under stamen).
• A priming-tube.
• A telescope, or that part of it into which the lenses are fitted.
• The barrel of a chain-pump.
• A small receptacle of drawn lead, of approximately tubular form, closed at the bottom by bending it over twice or three times on itself, and having a screw-cap at the top, used to hold pigments or similar matter in a semifluid condition.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To furnish with a tube.
• noun A hollow cylinder, of any material, used for the conveyance of fluids, and for various other purposes; a pipe.
• noun A telescope.
• noun A vessel in animal bodies or plants, which conveys a fluid or other substance.
• noun (Bot.) The narrow, hollow part of a gamopetalous corolla.
• noun (Gun.) A priming tube, or friction primer. See under Priming, and Friction.
• noun (Steam Boilers) A small pipe forming part of the boiler, containing water and surrounded by flame or hot gases, or else surrounded by water and forming a flue for the gases to pass through.
• noun A more or less cylindrical, and often spiral, case secreted or constructed by many annelids, crustaceans, insects, and other animals, for protection or concealment. See Illust. of Tubeworm.
• noun One of the siphons of a bivalve mollusk.
• noun (Elec. Railways), Chiefly Eng. A tunnel for a tube railway; also (Colloq.), a tube railway; a subway.
• noun a tube of very fine bore. See Capillary.
• noun (Steam Boilers) a tube which forms a flue.
• noun (Zoöl.) Same as Tubipore.
• noun (Zoöl.) one of the ambulacral suckers of an echinoderm.