立たち聞きく

godan verb (-ku)

eavesdrop; listen in

Intentionally listening to a conversation not meant for you, often while hiding nearby.

• 隣となりの部屋へやの話はなしを立たち聞ぎきしてしまった。

  I accidentally eavesdropped on the conversation in the next room.

• ドアの外そとで立たち聞きくのはやめなさい。

  Stop eavesdropping outside the door.