Source : Webster's Revised Unabridged Dictionary (1913)

Naphthol \Naph"thol\, n. [Naphthalene + -ol.] (Chem.)
   Any one of a series of hydroxyl derivatives of naphthalene,
   analogous to phenol. In general they are crystalline
   substances with a phenol (carbolic) odor.

   {Naphthol blue}, {Naphthol orange}, {Naphthol yellow}
      (Chem.), brilliant dyestuffs produced from certain complex
      nitrogenous derivatives of naphthol or naphthoquinone.

Source : WordNet®

naphthol
     n : either of two phenols derived from naphthalene