\Pyr"rol\, n. [Gr. ? flame-colored (from ? fire) + L.
oleum oil.] (Chem.)
A nitrogenous base found in coal tar, bone oil, and other
distillates of organic substances, and also produced
synthetically as a colorless liquid, {C4H5N}, having on odor
like that of chloroform. It is the nucleus and origin of a
large number of derivatives. So called because it colors a
splinter of wood moistened with hydrochloric acid a deep red.