/ Dictionary / Index P prothorax: Meaning and Definition of Find definitions for: pro•tho•rax Pronunciation: (prō-thôr'aks, -thōr'-), [key] — pl. -tho•rax•es, -tho•ra•ces the anterior division of the thorax of an insect, bearing the first pair of legs. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: prothorax (Thesaurus) prothoracic gland prothrombin Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language