Generally used by other gay guys to refer to the really-out-of-it trashy gay guys who partied a bit too hard and are now too out of it to know what's going on.
"Oh god, there's a DFQ in the restroom trying to wash his hands in the urinal..."
"The sun is coming up and the sunglasses are coming out; this place is getting a bit too DFQ; time to go home I think."
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi