Of a horse or other animal: having a depression or hollow in the back, esp. as a symptom of age or disease. Cf. saddleback, n. 2.

Of a horse: Having a depression in the spinal column, caused by strain. Also back-swayed, sway-backed, adj. Obsolete.

That has or forms a saddleback (in various senses of the noun). Cf. saddle-backed, adj.

Of an animal, esp. a horse: Having a downward curvature of the spinal column; strained in the back, as by overwork. Also transferred.

(of a horse) having a high ridged back.

Sway-backed.