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 ]

n. [ catechol + amine. ] any of a group of chemicals including epinephrine and norepinephrine that are produced in the medulla of the adrenal gland. They function as nerotransmitters in the sympathetic nervous system. Also, any structurally related chemical substance, whether natural or synthetic. [ WordNet 1.5 +PJC ]