The wing-flapping machine Leonardo da Vinci designed with spring-powered wings was an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, imitating the motion of birds or bats. Leonardo studied bird anatomy, wing movement, balance, and the mechanics needed to transfer human or stored energy into flapping motion. Some of his designs used frames, straps, and springs rather than a conventional propeller.
Leonardo’s notebooks contain multiple flying-machine concepts, and they do not describe one single finalized aircraft. His human-powered ornithopters would probably not have generated enough lift for sustained flight because human muscle power is limited compared with the power required to flap large wings.
The term is broader than Leonardo’s work: modern experimental ornithopters may use motors and remote control. Leonardo’s contribution was a detailed early investigation of mechanical flapping flight, not a successful man-carrying aircraft.