Variation of "xo", meaning 'hugs and kisses and fucks' (or kisses and hugs and fucks), as a sentimental farewell, seen in gay online chat or emails, usually after 'real-time' sex or hookup has occurred.
Guy # 1: "Hey stud, like I said, I had a great time last nite. Sorry I couldn't stay overnight. We gotta get 2gether again sometime soon."
Guy # 2: "Okay, dude, i'd like that too. cya, xof --rickster"