The fuckiest of the fucks, a "fuckboy" is the lowest possible form of the vile, degenerate waste pouring from the proverbial asshole of society. Calling some a fuckboy is the verbal equivalent of the orally penetrating their mother, their dog, and their girlfriend in the span of approximately 3.94 seconds, and is only to be used on people who make pre-school slurs like "fucker" and "cunt" look like tokens of sainthood.
JARRET: Hey, fuckboy!
COP: What did you just call me?
JARRET: I. Called. You. A. FUCKBOOOOOOOYYYYYYYYYY!!!!!!!