a viscid, blackish-brown liquid prepared by the destructive distillation of pine wood and used in the preparation of expectorants, disinfectants, tar paints, roofing materials, etc.
See pine tar in American Heritage Dictionary 4
noun
A viscous or semisolid brown-to-black substance produced by the destructive distillation of pine wood and used in roofing compositions and as an expectorant and antiseptic.