Short for “Sino Flying Object.” A quasi-symmetric (spherical, cylindrical, octagonal, …) object that has recently been spotted (or finally been detected) crossing near “US sensitive sites”—a few of them were shot down by a fighter
jet because they allegedly or exaggeratedly posed a surveillance threat to the security of the
country, or to the lives of the people.
The US had
shot three SFOs or UFOs in three days following the take down of a Chinese spy balloon that floated their sky the previous weekend, but they themselves had hypocritically launched no fewer than a dozen of these
slow-moving spy or surveillance objects over the Chinese or
Russian airspace since last year.