Unidentified

UFO stands for unidentified flying object.

"What does U.F.O. stand for?" "It means Unidentified Flying Object, I guess."

Have you ever seen an unidentified flying object?

We believed that the object was a UFO (Unidentified Flying Object).

After flying above the safe zone, the airplane went into unidentified air space.

Instead of ink, there was some unidentified liquid in the bottle.

There are about a hundred unidentified bodies to be buried.

Clyde Tombaugh's job was to photograph one small piece of the night sky at a time. He then had to carefully examine and compare the photos in an effort to detect an unidentified moving point of light that might be a planet.

Layla was shot by an unidentified attacker.

Last night he saw an unidentified flying object in the sky.