This is by no means official, but...
Spatial reasoning is what you use when you play Tetris or other fit-the-piece-in-the-hole type of games. It's what you use when looking at a collection of luggage and figuring out whether or not it will fit in your car or closet. It's what is used to estimate volumes of things, to estimate lengths and widths and such. It's what you use when someone else points somewhere, and you can tell where they're pointing even though you aren't the one behind their finger. It's what you use when you're leading a target in a flight sim, and what you use when you're guessing where a thrown object is going to land.