/yooh"ef"oh"/ or, sometimes, /yooh"foh/ , n. , pl. UFO's, UFOs .
any unexplained moving object observed in the sky, esp. one assumed by some observers to be of extraterrestrial origin. Also called unidentified flying object . Cf. flying saucer .
[ 1950-55; u ( nidentified ) f ( lying ) o ( bject ) ]