@DynamicSquid 4D is short for the 4th dimension. It's a (theoretical) axis that is perpendicular to all 3 axes of the 3rd dimension (our dimension).
Oh wow, I didn't even know this was a thing until I got mentioned. Thanks so much!! 😊
@DynamicSquid This doesn't happen in our dimension because there isn't enough space, but in higher dimensions, there is more space, meaning there could be an axis that is perpendicular to all the other axes.