Plain English Meaning
An update telling you whether a piece of restricted or special airspace is currently being used, when it will be used, or when it is free to fly through. It lets you know if you can cross that airspace or need to go around it.
Full Definition
Current information about whether a Special Use Airspace (SUA) area is active, scheduled to become active, or released, including the times of activity and any restrictions on flight within or near that airspace. It is provided to pilots so they can determine whether the airspace is hot (in use) or cold (not in use) before planning or conducting a flight near it.
Context Anchor
Pilots encounter this when checking special use airspace before or during a flight, usually through air traffic control, Flight Service, or published flight planning information.