/ Dictionary / Index P parallactic motion: Meaning and Definition of Find definitions for: par'allac'tic mo'tion Pronunciation: [key] — Astron. Astron. the apparent motion of stars due to the earth's orbital motion. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. parallactic ellipse parallax 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