Definition: White Hole

A white hole is a time-reversed black hole. It has been suggested that a collapsing black hole can be reversed to make a white hole, in which everything rushes out in an immense release of  energy.

This theory was popular in astronomical circles in the 1970's.

What happens when matter fall into singularity?

It emerges elsewhere in the universe as a white hole, at a different place and time, or perhaps even in another universe. However, there is no evidence that matter can be transported in this manner and the concept of white holes no longer seems tenable.

( Edward Harrison, Cosmology,  The Science of the Universe, 2nd edition, Cambridge Press.)