recurvation

from The Century Dictionary.

• noun The act or process of reeurving; the state of being curved up or back: opposed to decurvation: as, the recurvation of a bird's bill. Also recurvature recurvity.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of recurving, or the state of being recurved; a bending or flexure backward.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A bending or flexure backward.