Final answer:
The condition characterized by abnormally large jaws is Macrognathia and the action of the masseter is primarily for chewing.
Step-by-step explanation:
A condition characterized by abnormally large jaws is called Macrognathia. This condition can be contrasted with Micrognathia, which is characterized by abnormally small jaws. On the other hand, Bruxism refers to the grinding of teeth, often unconsciously, which can lead to various dental issues. Prognathism is a term used to describe a situation where a part of the jaw protrudes significantly, as is often noticed in comparison between the jaws of chimpanzees and humans, with the former having a more protruding jaw.
Regarding the action of the masseter, it is mainly responsible for chewing as it is a muscle that plays a crucial role in the movement of the mandible (lower jaw). It does not function in swallowing, moving the lips, or closing the eye. Its primary role is to elevate the mandible, which is essential for chewing food.