/ Dictionary / Index S symmetry plane: Meaning and Definition of Find definitions for: sym'metry plane" Pronunciation: [key] — Crystall. Crystall. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. symmetry element Symonds Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language