a star that has consumed so much of its energy that it no longer is able to release that energy and becomes overwhelmed by its own gravitational forces

Once a very large star collapses in on itself towards the end of its life, there is so much gravitational pull on the material, that not even the atoms inside the star can stop it from collapsing. The star then collapses back in on itself to create a blackhole from which not even light can escape.

Term describing what happens to email that is blocked without a bounce response to the sender.

an online database of computer addresses (IPs)