Which synovial joint movement is described as turning the sole outward away from the midline of the body?

Eversion.

Explanation:

Eversion is a special type of the body movement that makes the movement inside-out of the body. The opposite o the inversion is eversion.

This synovial joint movement turns the sole outward and away from the midline of the body. The joint movement of the body is also involved in the eversion process.

Thus, the correct answer is eversion.