Merriam-Webster Collegiate Dictionary - tube

 noun  Etymology: French, from Latin tubus; akin to Latin tuba trumpet  Date: 1651  1. any of various usually cylindrical structures or devices: as  a. a hollow elongated cylinder; especially one to convey fluids  b. a soft tubular container whose contents (as toothpaste) can be removed by squeezing  c.  (1) tunnel  (2) British subway b  d. the basically cylindrical section between the mouthpiece and bell that is the fundamental part of a wind instrument  2.  a. a slender channel (as a fallopian ~ or a pollen ~) within a plant or animal body ; duct  b. the narrow basal portion of a corolla with united petals or a calyx with united sepals  3. inner ~  4.  a. electron ~; especially vacuum ~  b. cathode-ray ~; especially a television picture ~  c. television  5. an article of clothing shaped like a ~ a ~ top ~ socks  • ~d adjective  • ~like adjective