\Xy"lene\, n. [Gr. xy`lon wood.] (Chem.)
Any of a group of three metameric hydrocarbons of the
aromatic series, found in coal and wood tar, and so named
because found in crude wood spirit. They are colorless, oily,
inflammable liquids, {C6H4.(CH3)2}, being dimethyl benzenes,
and are called respectively {orthoxylene}, {metaxylene}, and
{paraxylene}. Called also {xylol}.
Note: Each of these xylenes is the nucleus and prototype of a
      distinct series of compounds.