an (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins
An unidentified flying object.
An alien spacecraft.
Origin: Reading of UFO as a word in its own right.
UFO are an English heavy metal and hard rock band, who were formed in 1969. UFO became a transitional group between early hard rock and heavy metal and the New Wave of British Heavy Metal. UFO were ranked No. 84 on VH1's '100 Greatest Artists of Hard Rock'.