Question

fill in the blank question
veins that have become permanently distended and convoluted due to a loss of competence of the venous valves are known as □ veins.

Explanation:

In the context of medicine (a subfield of Natural Science), veins that are permanently distended and convoluted due to valve incompetence are defined as varicose veins. This is a standard medical term for such a condition.

Answer:

varicose