Flying saucer (library) definition

Flying saucer (library)

WordNet

(1) An (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins

WiktionaryText

An unidentified flying object; UFO; usually with disc-like properties.

Some connect the recent spate of flying saucer sightings with a rumored top-secret military aviation project.
In fiction, an alien interplanetary vessel with a disc-like shape and generally metallic appearance.