| UFO. |
[yoo-ef-oh or, sometimes, yoo-foh] 
| any unexplained moving object observed in the sky, esp. one assumed by some observers to be of extraterrestrial origin. |
| un·i·den·ti·fied flying object (ŭn'ī-děn'tə-fīd') n.
|
The abbreviation for unidentified flying object. Sometimes referred to colloquially as “flying saucers.” Most UFO sightings have prosaic explanations; there is no hard evidence that extraterrestrial beings are visiting Earth.