(idiomatic) To argue uncompromisingly with someone. They always seem to butt heads when they end up talking about politics.

What does butting heads mean?

Synonyms & Antonyms of butting heads

to express different opinions about something often angrily. Our boss tries not to schedule Rosie and Mark for the same shifts, since the two often butt heads.

What does it mean when two people but heads?

If you bang peoples' heads together or knock their heads together, you tell them off severely for doing something wrong or for not doing something they were asked to do.