UFO (Unidentified Flying Object)
I thought I saw a UFO, but it was really an airplane.
She told the police that a UFO abducted her in the middle of the night.
bury one's head in the sand
He had suspected for some months that his son was taking drugs, but he had buried his head in the sand and refused to admit it, even to himself.
I'm afraid I have to leave now.
I'm afraid you are wrong about it this time.