/ Dictionary / Index P prosthion: Meaning and Definition of Find definitions for: pros•thi•on Pronunciation: (pros'thē-on"), [key] — n. Craniom. the most forward projecting point of the anterior surface of the upper jaw, in the midsagittal plane. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: prosthion (Thesaurus) prosthetist prosthodontics Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language