/ Dictionary / Index E event horizon: Meaning and Definition of Find definitions for: event' hori"zon Pronunciation: [key] — Astron. Astron. the boundary around a black hole on and within which no matter or radiation can escape. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. eventful eventide Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language