An extremely psycho fucking girl. A Yuying is a guy in a woman's body. She tends to attack people because she is a beast. She also tends to talk like a fucktard and whenever people see her; they either laugh uncontrollibly or get heart attacks. A Yuying is a honger that acts "cool".
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