Source : Webster's Revised Unabridged Dictionary (1913)

Xylidine \Xy"li*dine\, n. (Chem.)
   Any one of six metameric hydrocarbons, {(CH3)2.C6H3.NH2},
   resembling aniline, and related to xylene. They are liquids,
   or easily fusible crystalline substances, of which three are
   derived from metaxylene, two from orthoxylene, and one from
   paraxylene. They are called the amido xylenes.

   Note: The xylidine of commerce, used in making certain dyes,
         consists chiefly of the derivatives of paraxylene and
         metaxylene.