unidentified flying object vs UFO

unidentified flying object and UFO both are nouns.

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

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

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

Other synonyms of unidentified flying object include flying saucer.

unidentified flying object (noun)	UFO (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