(also ufo ) / ˌjuː ef ˈəʊ; ˈjuːfəʊ; NAmE ˌjuː ef ˈoʊ; ˈjuːfoʊ/ noun
( pl. UFOs ) a strange object that some people claim to have seen in the sky and believe is a spacecraft from another planet (abbreviation for 'Unidentified Flying Object')
—compare flying saucer
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WORD ORIGIN
1950s: acronym from unidentified flying object .