some shiny things you wear around your neck. and your fingers. and your teeth aka "grillz". "Rob a jewelry store and tell em to make me a grill." Usually very blinding.
Bling is jewelry, if you blingin, juss means your iced out bruh. Its played out 4real though, no one really uses this worn no more, except white people. even old ladies and disney channel be saying bling bling. so dont say that shit, use somethin else.