Is it just me or is there too much confusion surrounding the term headbutt, not long ago we used the expression clash of heads. I think headbutt makes it sound deliberate, clash of heads decribes what happens in most cases.
In the past a referee would make reference to a headbutt when issuing a warning or deducting points for a deliberate act. Even the expression unintentional headbutt sounds bad.
Maybe it's just because I am from Glasgow !