Picoline \Pic"o*line\, n. [L. pix, picis, pitch + oleum oil + -ine.] (Chem.) Any one of three isometric bases ({C6H7N}) related to pyridine, and obtained from bone oil, acrolein ammonia, and coal-tar naphtha, as colorless mobile liquids of strong odor; -- called also {methyl pyridine}.