/ Dictionary / Index P pronephros: Meaning and Definition of Find definitions for: pro•neph•ros Pronunciation: (prō-nef'ros, -rus), [key] — pl. -roi -ra one of the three embryonic excretory organs of vertebrates, which becomes the functional kidney of certain primitive fishes. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. prone float prone pressure method Related Content Daily Word Quiz: opulent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language