Fake Jamaican, usually a Wigga. People who feel the need to act like a Jamaican because they smoke weed. People whose parents are born in Jamaica but they themselves were born in England and speak shit Patois when they get angry.
Jafaican is a dialect of English becoming more common in London's West End, within the tradition boundaries of the Cockney dialect: within the sound of the Bow bells and is slowly replacing Cockney. Jafaican is a mixture of English, Jamaican, West Indian and Indian language elements.
Some Jafaican, for you reading pleasure:
Safe, man. You lookin buff in dem low batties. Dey's sick, man. Me? I'm just jammin wid me bruds. Dis my yard, innit? Is nang, you get me? No? What ends you from then?