\To*lu"i*dine\, n. (Chem.)
Any one of three metameric amido derivatives of toluene
analogous to aniline, and called respectively
{orthtoluidine}, {metatoluidine}, and {paratoluidine};
especially, the commonest one, or {paratoluidine}, which is
obtained as a white crystalline substance.
Note: It is used in the aniline dye industry, and constitutes
      the essential nucleus or radical of those dyes.