Tar1  —n. 1 dark thick inflammable liquid distilled from wood or coal etc., used as a preservative of wood and iron, in making roads, as an antiseptic, etc. 2 similar substance formed in the combustion of tobacco etc. —v. (-rr-) cover with tar.  tar and feather smear with tar and then cover with feathers as a punishment. Tarred with the same brush having the same faults. [old english]