Ostentatious, over-the-top jewellery or dress. Often used to demonstrate the wearer's wealth.
This term came to prominence right at the end of the 20th century, when 'bling' became a central feature of the Gansta rap hip hop scene in the USA. It was also in use in Jamaica about the same time and it isn't clear where the term was coined. The first use of it in print is in the lyrics of 'Bling Bling', which was recorded in 1999 by the rap artist B.G. (a.k.a. 'Baby Gangsta', a.k.a. Christopher Dorsey), on the album Chopper City In The Ghetto:
... Big ballin' Calhounie's, you can see him when he comin' Booted up, diamond up Golds be shinin' up, all them diamonds be blindin' up ...
Bling bling Everytime I come around yo' city Bling bling Pinky ring worth about 50 Bling bling Everytime I buy a new ride Bling bling Lorenzos on Yokahama tires
The use of bling-bling in Jamaica is recorded in the Kingston newspaper The Gleaner, 18th December 1999. This was in a picture story about the Christmas decorations on a house on Portmore Parkway. Spelled out in coloured lights was: