横よこから口くちを挟はさむ

expression, godan verb (-mu)

butt into a conversation; interrupt; chime in

Used when someone not originally part of a conversation or discussion suddenly joins in, often with an unsolicited opinion. The phrase carries a nuance of intrusion from the side.

• 彼かれはいつも横よこから口くちを挟はさんでくる。

  He always butts into our conversations.

• 会かい議ぎ中ちゅうに横よこから口くちを挟はさむのはやめてください。

  Please stop interrupting during the meeting.