Singleton component
An ECS component that exists exactly once in the whole world and holds the global state that belongs to no particular entity.
Timothy Ford gave it its name in his GDC 2017 talk on Overwatch's gameplay architecture. In a strict entity component system systems carry no data of their own, yet something still has to hold keyboard input, the camera's state or the queue of pending network packets. The answer was to put that state in components attached to a single anonymous entity, so systems reach it the same way they reach everything else.
The point is not to avoid global state but to make it visible: which systems read and write which singleton can be seen and searched for, instead of lurking in static variables. Bevy calls the same thing resources, and Unity DOTS has singleton entities. Underneath it is still a singleton, just with a more honest label.