/ Dictionary / Index P Protagoras: Meaning and Definition of Find definitions for: Pro•tag•o•ras Pronunciation: (prō-tag'ur-us), [key] — n. c480–c421b.c.,Greek Sophist philosopher. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. protagonist protamine Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language