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]