What is a Black Hole in astronomical terms?

A Black Hole is defined as a point in space where gravity is exceptionally strong such that nothing, not even light, can escape its grasp. This intense gravitational pull occurs because a significant amount of mass has been concentrated into a very small area, typically resulting from the gravitational collapse of a massive star after it has exhausted its nuclear fuel.

The boundary surrounding a black hole is known as the event horizon; once crossed, escape is impossible, which is why they are termed "black" since they do not emit light. The unique properties of black holes lead to intriguing consequences in physics and cosmology, such as time dilation and the bending of light around them.

While some options may touch on related concepts, such as a dense planetary body or a dying star, they do not encapsulate the specific and defining characteristic of a black hole, which is the extraordinary gravity that defines its nature.