What is the ability of solid to flow?

Apparently rigid rock can indeed flow, given enough time. And with the appropriate applied forces of course.

In the south island of New Zealand where I live, the land has shrunk in an E - W direction by about 150cm over a length of about 200 km, in the 150 years of survey history. That is about 5mm per year per 100km. This is all plastic flow, and is building the local mountains higher.

If you look at a sedimentary sequence, you'll often see folds in the rock.

Hard crystalline rocks such as granite do not deform as easily. Sandstone and mud-stone are more easily deformed.