listen in

US /ˈlɪs.ən ɪn/
UK /ˈlɪs.ən ɪn/
"listen in" picture
1.

偷聽, 竊聽

to listen to a private conversation between other people, without them knowing that you are listening

:
I caught my sister trying to listen in on my phone call.
我發現我妹妹在偷聽我的電話。
The neighbors often listen in on our conversations.
鄰居們經常偷聽我們的談話。