a strange object that some people claim to have seen in the sky and believe is a spacecraft from another planet (the abbreviation for ‘unidentified flying object’) compare flying saucerTopics Spacec1不明飞行物,幽浮(全写为 Unidentified Flying Object) Oxford Collocations DictionaryUFO is used before these nouns:- sighting
Word Origin1950s: acronym from unidentified flying object.