That's because I made up the term. It's pretty clear what it means, though, isn't it?

Despite the term being made up, that there is something to the concept is strongly suggested both by the observed diversity in degree of gender dysphoria (making it pretty clear that the strength and nature of feelings about one's sex are graded), and the existence of agender/genderblank/genderfree/etc./etc. as a gender identity.

As with anything, one should hold only tentatively to the idea that the phenomenon exists. But it sure looks like it does.