Wockney is a portmanteau of the words 'Wog' and 'Cockney'.
It is a synonym of the term 'Jafaican' which is used to describe the accent used by London juveniles, mainly. This accent seems to be gaining popularity by people of all races in the capital, and will likely spell the end of the typical 'Cockney' accent that has been the traditional dialect for centuries.
It could also refer to the individual themselves.
"Why does Dizzee Rascal speak in that stupid Wockney accent?"