the surface around a black hole enclosing the space from which electromagnetic radiation cannot escape due to gravitational attraction. For a non-rotating black hole, the radius is proportional to the mass of the black hole
event horizon in American English
Astronomy
the spherical boundary surrounding a black hole, within which there is such strong gravity that nothing, not even light, can escape
Examples of 'event horizon' in a sentence
event horizon
It was as if a cosmic black hole had opened in the room behind us, just across the event horizon of its threshold.