Answer:
degenerate matter would be incompressible. This would not be ordinarily met with, but is considered to be the material of a neutron star. Where, upon the collapse of a giant star, the gravitational forces would collapse all the neutron matter to a solid.
Fond subject of sci-fi writers, e.g. Larry Niven (I think) wrote a story with the title Neutron Star, which will give a rough guide to the supposed physics.