noun - A drone or an unmanned aerial vehicle (UAV) is an aircraft without a human pilot on board. Drones are a component of an unmanned aircraft system (UAS); which include a UAV, a ground-based controller, and a system of communications between the two. The flight of UAVs may operate with various degrees of autonomy: either under remote control by a human operator or autonomously by onboard computers.
Compared to crewed aircraft, drones were originally used for missions too dull, dirty or dangerous for humans. While they originated mostly in military applications, their use is rapidly expanding to commercial, scientific, recreational, agricultural, and other applications such as policing, peacekeeping, and surveillance, product deliveries, aerial photography of open water swimmers and open water swimming events, smuggling, and drone racing. Civilian UAVs now vastly outnumber military UAVs.