The Collaborative International Dictionary of English v.0.48:

Tobacco \To*bac"co\, n. [Sp. tabaco, fr. the Indian tabaco the
   tube or pipe in which the Indians or Caribbees smoked this
   plant. Some derive the word from Tabaco, a province of
   Yucatan, where it was said to be first found by the
   Spaniards; others from the island of Tobago, one of the
   Caribbees. But these derivations are very doubtful.]
   1. (Bot.) An American plant (Nicotiana Tabacum) of the
      Nightshade family, much used for smoking and chewing, and
      as snuff. As a medicine, it is narcotic, emetic, and
      cathartic. Tobacco has a strong, peculiar smell, and an
      acrid taste.
      [1913 Webster]

   Note: The name is extended to other species of the genus, and
         to some unrelated plants, as Indian tobacco (Nicotiana
         rustica, and also Lobelia inflata), mountain tobacco
         (Arnica montana), and Shiraz tobacco (Nicotiana
         Persica).
         [1913 Webster]

   2. The leaves of the plant prepared for smoking, chewing,
      etc., by being dried, cured, and manufactured in various
      ways.
      [1913 Webster]

   Tobacco box (Zool.), the common American skate.

   Tobacco camphor. (Chem.) See Nicotianine.

   Tobacco man, a tobacconist. [R.]

   Tobacco pipe.
      (a) A pipe used for smoking, made of baked clay, wood, or
          other material.
      (b) (Bot.) Same as Indian pipe, under Indian.

   Tobacco-pipe clay (Min.), a species of clay used in making
      tobacco pipes; -- called also cimolite.

   Tobacco-pipe fish. (Zool.) See Pipemouth.

   Tobacco stopper, a small plug for pressing down the tobacco
      in a pipe as it is smoked.

   Tobacco worm (Zool.), the larva of a large hawk moth
      (Sphinx Carolina syn. Phlegethontius Carolina). It is
      dark green, with seven oblique white stripes bordered
      above with dark brown on each side of the body. It feeds
      upon the leaves of tobacco and tomato plants, and is often
      very injurious to the tobacco crop. See Illust. of Hawk
      moth.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Nicotiana rustica
    n 1: tobacco plant of South America and Mexico [syn: wild
         tobacco, Indian tobacco, Nicotiana rustica]