Why is bread a solid but still can be squashed?

Bread can be squashed fairly easily because the structure of bread is composed of spongy, flexible elements. But actually, with sufficient force all solids can be squashed. Some are harder to squash than others. The gravitational field of a black hole squashes all things that get too close to it. Solidity does not mean indestructibility, it just means that under normal circumstances, an object retains its shape.