Asphalt

A bituminous waterproofing agent used in various types of roofing materials.

Merriam-Webster Online Dictionary
asphalt (noun)
1.
a dark bituminous substance that is found in natural beds and is also obtained as a residue in petroleum refining and that consists chiefly of hydrocarbons
2.
an asphaltic composition used for pavements and as a waterproof cement
asphalt (verb)
transitive verb
to cover with asphalt - pave