The quality or state of being curved or bent; curvedness, curvature; (also) a curved portion of anything, a curve.

Medicine and Veterinary Medicine. Originally: abnormal curvature of the spine resulting in a convexity which is forward-facing (in a person) or…

Lateral curvature of the spine; distinguished from lordosis and cyphosis.

An abnormal or exaggerated curve in the spine; the condition (of the spine or part of the spine) of having such a curve.

Transverse or lateral curvature (of the spine).

(a) a very straight or stiff back (also attributive); (b) Medicine a rigid spine, esp. in ankylosing spondylitis; the disease itself.

= poker back n. (b).