mass - Point masses and infinite densities

Point masses are masses who don't have volume. It is said that they are infinitly dense, but I though division by zero is undefined hence you can't define the density for a point mass because $\rho=m/V$ (and at $V=0$ then $\rho$ is undefined)

So why do physicist like Stephen Hawking and Richard Feynman say that a point mass is infinitely dense?