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.
彼はいつも横から口を挟んでくる。
He always butts into our conversations.
会議中に横から口を
Please stop interrupting during the meeting.