/ Dictionary / Index D decay series: Meaning and Definition of Find definitions for: decay' se"ries Pronunciation: [key] — Physics. Physics. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. decay constant decay time Related Content Daily Word Quiz: nonchalant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language