The Collaborative International Dictionary of English v.0.48:

Pyrocatechin \Pyr`o*cat"e*chin\, n. [Pyro- + catechu.] (Chem.)
   A white crystalline substance, C6H4(OH)2, of the phenol
   series, found in various plants; -- so called because first
   obtained by distillation of gum catechu. Called also
   catechol, oxyphenol. etc.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

catechol \cat"e*chol\ (k[a^]t"[e^]*k[add]l`), n. [.]
   any of a group of chemicals having a benzene ring substituted
   with two hydroxyl groups in ortho position, especially
   ortho-dihydroxybenzene itself (C6H6O2), also called
   pyrocatechol, used in photography and as a reagent.
   [PJC]