butt in
verb1
Idiomatic, Informal To join a conversation or situation in which one is not welcome or invited; to interject (connotes a rude or discourteous interruption).
- Hey, this is none of your business; don’t butt in!
- Forgive me for butting in.
1 more example
- That spurt of rage took Bradly in the midriff before he could control it. He was standing over Podson with such eminent threat in his bristling beard that Podson said sulkily, "Oh, all right, I don't want to butt in, if you feel like that about it."1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, →OCLC, page 125:
2
Informal To join a queue not at the end, but in the middle, in violation of etiquette.