Lewis & Short

1. tŭbŭlus, i, m. dim. [tubus], a small pipe or tube, a water-pipe.

  1. I. Lit., Varr. R. R. 1, 8, 4; Vitr. 8, 7; Plin. 35, 12, 46, § 159.
    A smoke-pipe, Dig. 8, 2, 13.
  2. II. Transf., a bar of metal, a pig, ingot, Plin. 33, 6, 35, § 106.