/ Dictionary / Index T thiouracil: Meaning and Definition of Find definitions for: thi•o•u•ra•cil Pronunciation: (thī"ō-yoor'u-sil), [key] — n. Pharm. a white, slightly water-soluble, bitter, crystalline powder CHNOS, used chiefly in treating hyperthyroidism by reducing the activity of the thyroid gland. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thiouracil (Thesaurus) thiothixene thiourea Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language