UFO

名词 ufo:

1. an (apparently) flying object whose nature is unknown; especially those considered to have extraterrestrial origins
   同义词：unidentified flying object, flying saucer

1. Have any of you actually seen a UFO?
   你们中间是不是有人确实看到过飞碟？
2. No, it can not be a ufo.
   不，不可能是个不明飞行物。