UIUs
UIUs is a term that can refer to several different concepts depending on the context. One common meaning refers to Unidentified Unusual Objects, a category of phenomena that defies easy explanation through conventional means. These are distinct from Unidentified Flying Objects (UFOs) in that they do not necessarily exhibit flight characteristics. UIUs can encompass a wide range of observations, from strange lights in the sky that do not move like aircraft to anomalous ground-based or water-based phenomena.
In a different context, UIUs might stand for User Interface Units, a term used in software development
Another potential interpretation of UIUs relates to specific organizational acronyms. For instance, the University of Illinois