It means bastard. Originally used by bengali boys. It can also mean that if someone is a badman then they a funga.
That boys going on like hes funga
Something that only certain people know about and they talk about it all the time around people who don't know what it is and they have to figure it out.
-Dude that is funga!
-Man funga is da bomb.
-"I hit my head on the side walk today"... oh yeah? What'd funga have to say about it?