Tube  —n. 1 long hollow cylinder. 2 soft metal or plastic cylinder sealed at one end and holding a semi-liquid substance (tube of toothpaste). 3 hollow cylindrical organ in the body. 4 (often prec. By the) colloq. London underground (went by tube). 5 a cathode-ray tube, esp. In a television set. B (prec. By the) esp. Us colloq. Television. 6 us thermionic valve. 7 = *inner tube. 8 austral. Slang can of beer. —v. (-bing) 1 equip with tubes. 2 enclose in a tube. [latin]