Merriam-Webster Collegiate Dictionary - backboard

 noun  Date: 1761  1. a board placed at or serving as the back of something; especially a rounded or rectangular board behind the basket on a basketball court which serves to keep missed shots from going out-of-bounds and from which the ball can be made to rebound into the basket  2. a stiff board on which an injured person and especially one with neck or spinal injuries is placed and immobilized in order to prevent further injury during transport