[ yoo-ef-oh or, sometimes, yoo-foh ]
/ ˈyuˈɛfˈoʊ or, sometimes, ˈyu foʊ /

noun, plural UFO's, UFOs.

any unexplained moving object observed in the sky, especially one assumed by some observers to be of extraterrestrial origin.
Compare flying saucer.

Origin of UFO

1950–55; u(nidentified) f(lying) o(bject)
Also called unidentified flying object.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

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British Dictionary definitions for ufo

/ (sometimes ˈjuːfəʊ) /

abbreviation for

unidentified flying object
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Cultural definitions for ufo (1 of 2)

[ (yooh-ef-oh) ]

An abbreviation for “Unidentified Flying Object.” Often described as “flying saucers,” some UFOs are believed to come from other planets or galaxies and thus support the idea that human beings are not the only form of intelligent life in the universe. Few scientists agree.

Cultural definitions for ufo (2 of 2)

[ (yooh-ef-oh) ]

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.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.