Source : Webster's Revised Unabridged Dictionary (1913)

Developable \De*vel"op*a*ble\, a.
   Capable of being developed. --J. Peile.

   {Developable surface} (Math.), a surface described by a
      moving right line, and such that consecutive positions of
      the generator intersect each other. Hence, the surface can
      be developed into a plane.