Source : Webster's Revised Unabridged Dictionary (1913)

Tar \Tar\, n. [OE. terre, tarre, AS. teru, teoru; akin to D.
   teer, G. teer, theer, Icel. tjara, Sw. tj["a]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.

   {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.

Tar \Tar\, n. [Abbrev. from tarpaulin.]
   A sailor; a seaman. [Colloq.] --Swift.

Tar \Tar\, v. t. [imp. & p. p. {Tarred}; p. pr. & vb. n.
   {Tarring}.]
   To smear with tar, or as with tar; as, to tar ropes; to tar
   cloth.

   {To tar and feather a person}. See under {Feather}, v. t.

Source : WordNet®

tar
     n 1: any of various dark heavy viscid substances obtained as a
          residue [syn: {pitch}]
     2: a man who serves as a sailor [syn: {mariner}, {seaman}, {Jack-tar},
         {Jack}, {old salt}, {seafarer}, {gob}, {sea dog}]
     [also: {tarring}, {tarred}]

tar
     v : coat with tar; "tar the roof";  "tar the roads"
     [also: {tarring}, {tarred}]

Source : Free On-Line Dictionary of Computing

tar
     
         ("Tape ARchive", following {ar}) {Unix}'s
        general purpose {archive} utility and the file format it uses.
        Tar was originally intended for use with {magnetic tape} but,
        though it has several {command line options} related to tape,
        it is now used more often for packaging files together on
        other media, e.g. for distribution via the {Internet}.
     
        The resulting archive, a "tar file" (humourously, "tarball")
        is often compressed, using {gzip} or some other form of
        compression (see {tar and feather}).
     
        There is a {GNU} version of tar called {gnutar} with several
        improvements over the standard versions.
     
        {Filename extension}: .tar
     
        {MIME type}: unregistered, but commonly application/x-tar
     
        {Unix manual page}: tar(1).
     
        Compare {shar}, {zip}.
     
        (1998-05-02)