The Collaborative International Dictionary of English v.0.48:

Pyridine \Pyr"i*dine\, n. [From Gr. ? fire.] (Physiol. Chem.)
   A nitrogenous base, C5H5N, obtained from the distillation
   of bone oil or coal tar, and by the decomposition of certain
   alkaloids, as a colorless liquid with a peculiar pungent
   odor. It is the nucleus of a large number of organic
   substances, among which several vegetable alkaloids, as
   nicotine and certain of the ptoma["i]nes, may be mentioned.
   See Lutidine.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pyridine
    n 1: a toxic colorless flammable liquid organic base with a
         disagreeable odor; usually derived from coal