/ Dictionary / Index T thyroxine: Meaning and Definition of Find definitions for: thy•rox•ine Pronunciation: (thī-rok'sēn, -sin), [key] — n. the thyroid gland hormone that regulates the metabolic rate of the body. a commercial form of this compound, obtained from the thyroid glands of animals or synthesized, used in the treatment of hypothyroidism. Symbol: T Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thyroxine (Thesaurus) thyrotropin-releasing hormone thyrse Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language