/ Dictionary / Index W worldline: Meaning and Definition of Find definitions for: world'line' Pronunciation: [key] — Physics. Physics. (in relativity) the path of a particle in space-time. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. World Health Organization worldling Related Content Daily Word Quiz: candor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language