A technique done by linemen in the sport of football to deliver devastating blows by using their forearms on the opposing team. Players wore big forearm pads that went out over their elbows and they would practice their craft by thrusting their forearmsinto blocking bags. Some guys would go so far as to ram their forearmsinto walls.
"Yo, that dude just clocked the QB with a forearm shiver."
"The ref went ballisticafter he was forearm shivered by the 300 pound lineman."