It stands for Unidentified Flying Object. UFO. Alien or alien ship.
Flying object not yet identified, which could be observed from the ground in some constellation and that thanks to the uncertainty principle we can specify its position but not its speed, and its speed but not its position.
Better known as UFO (Unidentified Flying Object ) or UFO ( object flying identified ) refers to a form of saucer ship apparently Royal origin and nature unknown.