The term "mutton quad" is a somewhat outdated phrase that refers to the muscle at the front of the upper leg in sheep or lamb. If you're looking for synonyms for this specific term, there aren't many options. However, if you're looking for other ways to describe this muscle group, there are several possibilities. The most common term for this muscle group is simply the quadriceps. Other options include the thigh muscles or the front leg muscles. Depending on the context, specific terms like the vastus lateralis or the rectus femoris may also be used to refer to different parts of this muscle group.