What does "saucer" mean?

Additional senses

1. 2.Something resembling a saucer in shape. Specifically: (a) A flat, shallow caisson for raising sunken ships. (b) A shallow socket for the pivot of a capstan. Flying saucer, a type of Unidentified Flying Object, having a biconvex discoid shape; such objects are occasionally reported to have been sighted, but no example of one has been reliably shown to exist. They are believed by ufologists to originate in outer space, but they are generally presumed to be misinterpretations of ordinary phenomena, illusions or imaginary objects. Fraudulent photographs purporting to show flying saucers are published from time to time.