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]