unidentified flying object vs flying saucer

unidentified flying object and flying saucer both are nouns.

Word	Noun	Adjective	Verb	Adverb
unidentified flying object	Yes	No	No	No
flying saucer	Yes	No	No	No

As nouns, unidentified flying object and flying saucer are synonyms defined as:

unidentified flying object and flying saucer: an (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins

Other synonyms of unidentified flying object include UFO.

unidentified flying object (noun)	flying saucer (noun)
an (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins	an (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins