It's not called anything because it doesn't really exist, it is outside the horizon of events. Think of it same way as about volume which is inside a black hole

It's not called anything because it doesn't really exist, it is outside the horizon of events. Think of it same way as about volume which is inside a black hole. It doesn't exist... until you get there. Then the world outside the hole will become nonexistent to you, exactly same way as the area 'outside the universe' is to us now. Because the black hole will become your universe. In a way, we are sitting in a giant black hole.