Solidity

Part of speech: noun (n.)

1. The state or quality of being solid; density; consistency, -- opposed to fluidity; compactness; fullness of matter, -- opposed to openness or hollowness; strength; soundness, -- opposed to weakness or instability; the primary quality or affection of matter by which its particles exclude or resist all others; hardness; massiveness. That which hinders the approach of two bodies when they are moving one toward another, I call solidity. Locke.

2. Moral firmness; soundness; strength; validity; truth; certainty; - - as opposed to weakness or fallaciousness; as, the solidity of arguments or reasoning; the solidity of principles, triuths, or opinions.

3. The solid contents of a body; volume; amount of inclosed space.

Synonyms: Firmness; solidness; hardness; density; compactness; strength; soundness; validity; certainty.