/ Dictionary / Index Z zeroth: Meaning and Definition of Find definitions for: ze•roth Pronunciation: (zēr'ōth), [key] coming in a series before the first: the zeroth level of energy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: zeroth (Thesaurus) zero-sum game zeroth law of thermodynamics Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language