Final answer:
Buon fresco is the term used to describe the frescoes that decorated the walls of Roman halls and villas.
Step-by-step explanation:
The term that can be used to describe the frescoes that decorated the walls of Roman halls and villas is buon fresco. Buon fresco is a painting technique that involves applying wet paint to wet lime plaster. As both components dry, a chemical reaction causes them to fuse together, making the painting part of the wall. Roman painters often used buon fresco as the primary method of decorating interior spaces, and many examples of these frescoes can be found in the remains of Roman houses and villas around Mt. Vesuvius.