The term headbutt...

[killersheep]

fig. A - Headbutt

http://www.youtube.com/watch?v=wCptkmM6THw

I get what you're saying, I will try to stick to "clash of heads" although
intentional or not it's still a headbutt.

[Kenneth B]

Good point. The distinction is important. Headbutt = possible DQ.
Clash of heads/unintentional headbutt = Possible nocontest

[Spicoli]

May just come down to malice as opposed to a risk run in every fight.How often do you here "A headbutt occured" rather that "He headbutted him".....its already phrased as intentional.Some guys lead with the head and some lead with the chin.

There are many times when you see a purposful,blatant butt.Agapito Sanchez comes to mind,saw T Reid do it. or this guy
http://www.youtube.com/watch?v=zgDBcbHpaMg

[donnydarkoIRL]

Glad to hear the Saddo faithful understand

[Howlin Mad Missy]

well in both terms the heads do clash but 'headbutt' for some implies an intention to do so.