/ Dictionary / Index H hyperthyroidism: Meaning and Definition of Find definitions for: hy•per•thy•roid•ism Pronunciation: (hī"pur-thī'roi-diz"um), [key] — n. Pathol. overactivity of the thyroid gland. a condition resulting from this, characterized by increased metabolism and exophthalmos. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: hyperthyroidism (Thesaurus) hyperthyroid hypertonia Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language