noun
interruption; interference; butting in
Refers to unsolicited interference or a remark made from the sidelines, often disrupting a conversation or plan. Commonly used in the phrase 横槍を入れる (to butt in).
会議中に彼が横槍を入れてきた。
He butted in during the meeting.
二人の話に横槍を入れないでくれ。
Don't interrupt our conversation.
Compound of 横 (side) and 槍 (spear), literally 'side spear'. The figurative meaning of interruption comes from the image of thrusting a spear in from the side.