The term 'Palindromic Copter Part' refers to the ROTOR of a helicopter, which is a five-letter word. The ROTOR is a component of the helicopter that provides lift and thrust, allowing the aircraft to move through the air. It consists of two or more blades that spin around a central hub, creating an airflow that generates lift. The ROTOR is powered by an engine, usually located in the fuselage of the helicopter.