solidity

What it means

1. countableuncountableThe state or quality of being solid.

   The human figures in the foreground, who stand out from the canvas with lifelike truth and solidity.

   1918, James George Frazer, Folk-Lore In The Old Testament, volume 1, page 135

   1 more example

   If colours, sounds, tastes, and smells be merely perceptions, nothing we can conceive is possest of a real, continu'd, and independent existence; not even motion, extension and solidity, which are the primary qualities chiefly insisted on.

   1739, David Hume, “Book 1, part 4, section 4”, in Treatise of Human Nature

2. countableuncountableMoral firmness; validity; truth; certainty.
3. countableuncountablegeometryThe solid contents of a body; volume; amount of enclosed space.

In a sentence

If colours, sounds, tastes, and smells be merely perceptions, nothing we can conceive is possest of a real, continu'd, and independent existence; not even motion, extension and solidity, which are the primary qualities chiefly insisted on.

1739, David Hume, “Book 1, part 4, section 4”, in Treatise of Human Nature

Where it comes from

1. Latinsoliditās
2. Middle Frenchsolidité
3. Englishsolidity

From solid + -ity, from Middle French solidité, from Latin soliditās.