The term ROTOR is a 9-letter crossword solution that can be used to describe a PROPELLER. A rotor is a type of mechanical device that uses a spinning motion to generate lift or thrust, and is commonly found in aircraft, helicopters, and wind turbines. It is also used in some types of watercraft, such as hovercrafts and submarines. The rotor is typically made up of several blades that rotate around a central hub, and the rotation of the blades creates a force that propels the vehicle forward.