Though there's probably a difference between androgynous and androgyny and androgyne, I'm too naive and uninformed to be so clever.
In my opinion, it's the way someone is. A few (yet unmentioned, I b'lieve) possibilities:
*Someone who, perhaps, doesn't focus at all on any sort of a gender/sex-related identity
*Someone who, perhaps, doesn't focus at all on any sort of an orientation-related identity
*Someone who, perhaps, unintentionally dresses and/or behaves in a way specific to no particular sex/gender
I've noticed that in my case, androgyny has been very unintentional. I remember friends back in middle and high school calling me androgynous and I'm confronted with very confused people on a weekly basis, who either ask me if I'm "a boy or a girl" or who assume (wrongly), which is just as good a confirmation that I could be one sex/gender or the other. My physical appearance is more associated with music scenes based in the 80s than with anything sex/gender/orientation-related. I think that's what confuses people the most (beneath a long, red trench coat, you can't see any bumps or shapes - practical, no?).