Jowls are excess flesh around the jaw and cheeks that tends to grow as people get older. The jowl is also the lower jaw, which is hinged so the mouth can open, in vertebrates.
The two meanings of jowl both relate to the jaw. In some cases, jowl literally means jaw, as in the hinged lower jaw of vertebrates. Without a jowl, you wouldn't be able to open your mouth. The jowl can also be called the jawbone, lower jawbone, mandible, or submaxilla. The other kind of jowl — usually called jowls — are loose, fleshy areas around the jaw and lower cheeks. Older people are more likely to have jowls, especially if they are overweight.