The Collaborative International Dictionary of English v.0.48:

Tar \Tar\, n. [OE. terre, tarre, AS. teru, teoru; akin to D.
   teer, G. teer, theer, Icel. tjara, Sw. tj[aum]ra, Dan.
   ti[ae]re, and to E. tree. [root]63. See Tree.]
   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.
   [1913 Webster]

   Coal tar. See in the Vocabulary.

   Mineral tar (Min.), a kind of soft native bitumen.

   Tar board, a strong quality of millboard made from junk and
      old tarred rope. --Knight.

   Tar water.
   (a) A cold infusion of tar in water, used as a medicine.
   (b) The ammoniacal water of gas works.

   Wood tar, tar obtained from wood. It is usually obtained by
      the distillation of the wood of the pine, spruce, or fir,
      and is used in varnishes, cements, and to render ropes,
      oakum, etc., impervious to water.
      [1913 Webster]