tar

Dark brown or black viscous liquid obtained by the destructive distillation of coal, shale, and wood. Tars consist of a mixture of hydrocarbons, acids, and bases. Creosote and paraffin oil are produced from wood tar. See also coal tar.

tar

In computing, a compression routine in common use on the Internet. Originally developed for Unix operating systems, the tar utility archives files and directories by grouping them together into one large file, which can then be compressed and stored off-line. It is often used to distribute software for Unix systems, and tar files bear the extension .tar. A file with the extension tar.Z is a tar archive that has also been compressed with the Unix compression utility.