Like a regular stab but is preformed at such an angle that it conceals the stab from any passing police (who would probably not dare get involved anyway).
A Gypo Stab can only be preformed with certain 'weapons'. Such as: a small lock/pen knife, a stick (sharpened by the pen knife which has been left in the caravan), a piece of scrap metal, or a fork.
More often than not the stab wound is not life threatening but is usually followed by a 'kicking in' or getting attacked by illegaly bred dogs.
Dick 'you were lucky, im supprised he didn't gypo stab you'
Harry 'might have forgotten his fork'