Tube

n. [Fr. tube, It. & Sp. tubo, Lat. tubus.]

1. A hollow cylinder, of any material, used for the conveyance of fluids, and for various other purposes; a pipe; a conduit.
2. A telescope. “Glazed optic tube.” Milton.
3. A vessel of animal bodies or plants, which conveys a fluid or other substance.
4. (Bot.) The narrow, hollow part of a monopetalous corall, by which it is fixed to the receptacle.
5. (Gun.) A small pipe used for discharging a cannon. See PRIMING-TUBE and FRICTION-TUBE.
6. (Steam-boilers.) A small pipe containing water, and surrounded by heated gases, in distinction from flue, which is a passage for gases.

Capillary tube, a tube of very fine bore. See CAPILLARY.—Tube of safety, a safety-tube. See SAFETY-TUBE.