From Longman Dictionary of Contemporary EnglishUFOUFO /ˈjuːfəʊ, ˌjuː ef ˈəʊ $ -foʊ, -ˈoʊ/ noun [countable] TTSTTA (unidentified flying object) a strange object in the sky, that some people believe is a spaceship from another world SYN flying saucer
Examples from the Corpus
UFO• Teacher, that is a UFO?• Coastguards, police and the Lerwick Observatory received 17 independent reports of a UFO.• Is this an encounter with a UFO?• The genuine effects are reproducible; the quirky - such as UFO sightings - are filed away but rarely prove significant for science.• Holloman was the supposed site of a famous UFO encounter, the one that Close Encounters was based on.• Jason says UFO is his favourite night of the week.• They had chosen to sign up with the UFO subculture. 