thiouracil

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A white crystalline compound, C₄H₄N₂OS, that interferes with the synthesis of thyroxine, used to reduce the action of the thyroid gland, especially in the treatment of hyperthyroidism.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry Any of a class of heterocycles based on 2-thioxo-1H-pyrimidin-4-one; the parent compound interferes with the synthesis of thyroxine and is used in the treatment of hyperthyroidism

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun depresses the function of the thyroid gland