AKA: The cowgirl position, which we can't name as such because the tag is used for actual cow girls.
These two seem relatively equivalent. Though straddling should technically be a more general and not necessarily sexual term, the fact is that I've gone through twenty five pages of "straddle -girl_on_top" and found not a single image that wasn't a cowgirl position.. Even the wiki articles for both say that they are just that.
Alias? Mass edit?
Updated by 0xCCBA696