A headbutt is a strike using the harder part of your head against the softer bones of the opponents face.
Generally you use the top of your head down to the crown (the area where a crown would fit on your head). When using your forehead, the hairline is a good guide.
The primary risk of using a headbutt is that you may accidentally miss your intended target, smashing your head into the hard part of your opponents head, damaging you as much as your opponent. Even when done correctly you may experience some negative effects.
Even so the headbutt is a powerful tool. It can generate a tremendous amount of power and when successful, can easily knock out an opponent (as you can see in the clips below). It is an unexpected strike which may catch your opponent completely off guard.
Not Clinched
*Mobster headbutts reporter
Clinched
Ground
