Headbutt (頭突き, Zudzuki) is a basic fighting technique.
The user of the technique must put the neck back, and then move it strongly forward, attacking his opponent face with a head or just causing their heads to collide. Although this technique does not require special martial arts skills and is typically based on brute force, even martial artists sometimes use it in matches because it is very effective.
During the first series, Doppo Orochi used a headbutt to break a concrete pipe. Even the great master, Gouki Shibukawa, used it against Doppo during their fight in the Underground Arena. In the second manga series, Baki Hanma used this technique in his fight with Sikorsky. Later Kaiou Jyaku used the technique on Kaiou Retsu but with the back of his head. In a more defensive purpose, Doppo used the technique against Kiyosumi Katou to break his finger in the fifth series of the manga.
Chiharu Shiba created his own version of this technique, hitting his opponents with his own face rather than with his forehead. In the first series, Retsu used the top of his head against Baki Hanma.