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.
You had a really scatty batty last night after i shat on you and then proceeded to bum fuck you.
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.
"Man, me and Tom were just scatty doobin all night."
"Unlucky mate, I got some high grade shit."
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.