Bullnecked describes someone — or an animal — with a short, very thick neck, like a bull’s. You hear it about strong men, guards, boxers, rugby players; it paints a body that looks heavy and powerful in the shoulders and neck. It can also be used of cattle and dogs. Though actually, said about a person it often feels rough, even unkind, as if you are judging their shape. It is descriptive, a little old-fashioned in careful writing, and you may also see it written bull-necked.