The Hofmeister Kink is a small inward kink at the base of the C-Pillar. As the C-Pillar slopes back towards the trunk of the car, right before it would normally end, it kinks back inward.
Named after BMW design director, Wilhelm Hofmeister, the famous Kink first debuted on the 1961 BMW 1500, which was part of the “Neue Klasse” of BMW vehicles.