Is a black hole still considered a star?
The definition of a star in astronomy/astrophysics is a ball of gas, compressed by gravity to such an extend that nuclear fusion is generated. As a byproduct of that, energy is released in the form of radiation and light.
A black hole IS compressed by gravity in the extreme to such an extent that it is neither formed by gases anymore nor produce nuclear fusion. It also does not produce light and it's only output is Hawking Radiation, so, once it collapses in on itself, it does not conform to the definition of a star any longer.