The quality or state of being firm or strong in structure. The solidness of the bridge was reassuring to the engineers.
The quality of being reliable or dependable. Her solidness as a team leader earned her the respect of her colleagues.
The state of being without holes or gaps; density. The solidness of the material made it ideal for construction purposes.
The state of a substance being in the solid phase rather than liquid or gas. Heating the ice reduced its solidness until it began to melt.