It means, Hell Yeah, Fucking Right. It comes from Drake's kit song, HYFR. Most commonly used on Facebook and Twitter, this abbreviation has just recently become known. Mostly used by wanna-be gansters and thugs.
Ayy brah, d'you see that hottie at the beach yesterday?!
af WhoCares17 30. november 2011
Stands for "Hell Ya Fucking right" One of Drakes song "HYFR" Take Care'
Girl: Do you love this shit? Are you high right now? Do you ever get nervous? Are you single? I heard you fucked your girl, is it true? You getting money? You think them niggas you with is with you?
af DrakeIsYourDADDi 21. november 2011