無む駄だ口ぐちを叩たたく

expression, godan verb (-ku)

chatter pointlessly; waste one's breath

Used for idle talk that serves no purpose, often with a negative connotation of being unproductive or annoying.

• 会かい議ぎ中ちゅうに無む駄だ口ぐちを叩たたいてはいけない。

  Don't chatter pointlessly during the meeting.

• 彼かれはいつも無む駄だ口ぐちを叩たたいてばかりいる。

  He's always just wasting his breath.