A fork of Rural Dictionary
This, rather crudely, is what happens when you masturbate a woman who is menstruating. I first heard it in Northern Ireland, which, I imagine, is its obvious place of origin and relates to the Ulster flag.
'Don't go there!' 'Why?' 'You'll get the red hand of ulster!'
A northern irish tradition of, when your friend turns his back, SLAP HIM ON THE BACK OR ASS AT F U L L FORCE. If you have a Northern irish friend watch ye back
I just gave ya the old red hand of ulster!