It's not supposed to be that hard to figure out if something is liquid or if something is solid. If it flows like water, it's liquid. If it stays relatively still, it's solid. But what if it's a substance that breaks the laws of normal behavior and is both liquid and solid? Like non-Newtonian fluids?
Non-Newtonian fluid, like the combination of cornstarch and water above, can be impossibly thick liquid or a very giving solid, depending on your half full, half empty perspective. Non-Newtonian fluids include everyday items like ketchup, toothpaste, blood, shampoo, paint and other things. It's all about the viscosity.
The Discovery Slow Down explains that the particles in non-Newtonian fluids are so large that when force is applied to it, "they have no time to move, creating a solid". Look how this liquid can support a bowling ball like a solid: