A thick, black, viscous liquid obtained by the distillation of wood, coal, etc., and having a varied composition according to the temperature and material employed in obtaining it.(noun)
source: webster1913
verb (v)
coat with tar(verb.contact)
Example: Tar the roof.
Tar the roads.
source: wordnet30
To smear with tar, or as with tar; as, to tar ropes; to tar cloth.(verb)