Question

define white hole...​ ​

Answer 1

White hole is the exact opposite concept of black hole. As we know black hole eats everything in it's path it capture even light.

White hole is the exact opposite concept that if black hole takes everything in then another hole should be there which emittes energy and mass. It's just a concept but there is no proof as we have for black hole.

Answer 2

In general relativity, a white hole is a hypothetical region of spacetime and singularity which cannot be entered from the outside, although energy-matter, light and information can escape from it. ... White holes appear in the theory of eternal black holes.