Head Slip is a technique used to avoid punches aimed for the head by swaying it to either the left or right of the oncoming blow.
It has been used by several boxers and was showcased as a way to neutralise "head-hunters". Sendō used this technique in his spar with Miyata with an open guard stance, relying on his instincts to dodge the punches, it was also used to dodge Motionless Jabs.