butt 1 
(bŭt)
(bŭt)v. butt·ed, butt·ing, butts
v.tr.
To hit or push against with the head or horns; ram.
v.intr.
1. To hit or push something with the head or horns.
2. To project forward or out.
n.
Phrasal Verbs: A push or blow with the head or horns.
butt in
1. To interfere or meddle in other people's affairs.
2. To interrupt the conversation or activity of other people.
3. To move into a line of people or things out of turn.
butt out Slang
To disengage from a matter involving another person.
[Middle English butten, from Old French bouter, to strike, of Germanic origin; see bhau- in the Appendix of Indo-European roots.]
butter n.