What is a singularity in physics

(physics) A point or region in spacetime in which gravitational forces cause matter to have an infinite density; associated with Black Holes

Usually the same as it is in mathematics. Either an infinity in the numerator, or one in the denominator.

Also, another name for a black hole.

A point where the equations that describe what's going on break down and nobody knows what happens.

it's scifi no evidence at all they actually exist