Abbreviation for "Unidentified Flying Object". The USAF defines a UFO as: Anything that relates to any airborne object which by performance, aerodynamic characteristics, or unusual features does not conform to any presently known aircraft or missile type, or which cannot be identified as a familiar object. (USAF Regulation 200-2)
The Mutual UFO Network (MUFON) is the world's largest civilian UFO scientific reseach organization.
by ufologist February 6, 2005
Unidentified Flying Object. Has evolved from a simple military classification to a word synonomous with aliens, Roswell, conspiracy theories, and general paranormal nuts.
It's a UFO! Oh, wait, it's an airplane. Or a pie plate. Or a crazy person.
by Disco Stu December 8, 2004
Unequivocally Fucked Over. Being so incredibly screwed that nothing will even compare to how screwed you are.
by Koldhart101 June 10, 2013
The sexual act in which a man performs on a woman (preferably someone's mother). First all the lights are turned off for total darkness. Next the man slips a glow-in-the-dark condom over his penis and then begins to float around the dark room; thus giving the effect of a flying spaceship, or other un-identified floating object. The woman then is invited to catch such object with whatever she pleases, i.e. her mouth or other orifices. When the man grows weary of floating around, he then proceeds to crash-land his "ship" into the woman's "Area51”.
"Hey Mitch, I totally UFO 'd your mom last night ! "
"She always loves when I crash my UFO in her. "
by Matty58 March 27, 2008
Unidentified Frozen Object. When you defrost a freezer sometimes you find a UFO that has been there for a long time.
We defrost our freezer once a year and we discard any UFOs
by kshell April 10, 2010
University of Oregon. The locals say "U of O" and to outsiders it just sounds like "UFO". I miss Eugene.
Oregonian: "Yeah, i went to school at the UFO"

Non-Oregonian: "What? You're an alien?"

Oregonian: sigh... -_-
by Ihatetheeastcoast January 21, 2010