Unidentified flying object

Airborne, submerged, and transmedium phenomena considered unusual and unidentified

An unidentified flying object (UFO), or unidentified anomalous phenomenon (UAP), is any perceived airborne, submerged or transmedium phenomenon that cannot be immediately identified or explained. Upon investigation, most UFOs are identified as known objects or atmospheric phenomena, while a small number remain unexplained.

This keyword could refer to multiple things. Here are some suggestions: