Butt heads is a slang term used to describe two people who are in disagreement or conflict with each other. The crossword solutions for this term are SPAR (4 letters), TUSSLE (6 letters), and CLASH (5 letters). SPAR refers to a light fight or boxing match, while a TUSSLE is a more physical altercation. A CLASH is a heated argument or disagreement. All three words can be used to describe the behavior of two people who are butt heads.