what is the name for a flashing above a window
It's called a drip cap.
transom is a bean a window over a door is called a fanlight A Transom IS indeed a window over a door
rear window defroster light keeps flashing
The flashing is probably "legally" the flashing and the window is the window. The fact that you can differentiate between the two means that the two are probably "legally" different. Just like there is a door and a door jamb; they don't really work without each other, but they are not "legally" the same thing or all one.
Because it is flashed in
The thing that hangs over any window to keep the sun out is called an awning.
Siding that is flashing alongside windows is commonly called the trim. However, it also can be called molding or PVC.
A hinged window is called a casement window.
phototropism
Lintel : Horizontal beam used as a finishing piece over a door or window.
If it suddenly popped up on your screen then that is potentially a virus IF you click it. Just click the red X on the flashing window and it should go away. But whatever you do, DO NOT click it. To prevent this from happening again, make sure you have a working pop-up blocker.
That is called photosensitive epilepsy. It is a form of epilepsy in which seizures are triggered by visual stimuli such as flashing lights.