The sexual act of shitting on anothers ass(batty)and smearing it all over or to use your own faecaes and do the same. usually during scat sex or solo masturbation.
Doobin refers to the act of smoking a 'doob' or 'spliff'. Scatty refers to the said doob being unsatisfactory or of bad quality. So scatty doobin means smoking a low quality spliff.
A real dirty scatty bitch / norse, can be used against anyone who has a slight discolouration to skin or clothes, usualy on the wiffy side, needless to say there's a few scatty bitches out there.