/ Dictionary / Index Z zero gravity: Meaning and Definition of Find definitions for: ze'ro grav'ity Pronunciation: (zēr'ō-jē'). [key] — Physics. Physics. the condition in which the apparent effect of gravity is zero, as in the case of a body in free fall or in orbit. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. zero-emission vehicle zero hour Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language