Unpleasant form of
assault: a
blade is used to cut two small nicks in each corner of the
victim's mouth (where the top and lower lips meet). This in itself isn't too bad, but the following knee to the
victim's
groin causes them to grimace or cry out in
pain, and consequently tear the flesh of their cheeks up to the ear, giving them the grisly "
Chelsea Grin".
I've no idea if this works, but it was often threatened in
school. The
concept certainly works
visually.
The
Chelsea connection may have something to do with the practice being
invented by followers of
Chelsea football club.