/ Dictionary / Index P periodic decimal: Meaning and Definition of Find definitions for: pe'ri•od'ic dec'imal Pronunciation: (pēr'ē-od'ik, pēr"-), [key] — Math. Math. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. periodical cicada periodic function Related Content Daily Word Quiz: belligerent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language