Leonardo da Vinci’s human-powered bird-wing flying-machine concept was an ornithopter.
An ornithopter is an aircraft designed to fly by flapping wings, rather than by using fixed wings or a rotating rotor. Leonardo studied birds and bats and sketched several machines in which a pilot would power wing movements with levers, pedals, or other mechanical linkages.
Leonardo’s designs were theoretical rather than successful aircraft. Human muscles cannot provide enough sustained power for a person-sized flapping machine to take off and remain airborne, a problem that Leonardo could not solve with Renaissance materials and mechanics.
The term is broader than Leonardo’s work: modern engineers have built small experimental ornithopters, including radio-controlled models. Leonardo’s flying sketches also included the aerial screw and a parachute, but those belong to different aerodynamic concepts.