retractility

/ˌriːtrækˈtɪləti/
noun
  1. The ability to be drawn back or pulled in, especially of a body part or object.
    • The retractility of the turtle's head into its shell is a key defense mechanism.
    • The retractility of a cat's claws helps it climb trees and catch prey.
    • Engineers studied the retractility of the landing gear to ensure it would fold smoothly into the plane.