Sway-backed is a term used to describe an animal, especially a horse, that has a sagging back due to old age, injury, or poor conformation. There are many synonyms that can be used instead of sway-backed, including dropped back, hollow back, and lordotic. Other terms that can be used to describe the same condition include roached back, high withers, or even just a bad back. Regardless of the term used, it's important to note that a sway-backed horse may still be functional and capable of performing many tasks, although certain activities like jumping may be more difficult for them.