An attractive person of indeterminate gender who appears to have the "XXY" chromosome arrangement. Most often used to describe women who, though fashionable and made-up, look a bit manly.
To which I add:
Popularized by the They Might Be Giants song about hermaphrodites. Unfortunately , a lot of people who heard the song didn't actually listen to the lyrics, and think 'sexxy' is just a synonym for sexy.
Did you see the woman in the skin-tight Versace dress with the big adam's apple? SeXXY.