listen in

listen in (third-person singular simple present listens in, present participle listening in, simple past and past participle listened in)

1. To listen without participating.

   Do you mind if I listen in on your meeting tomorrow?

   We invite you to listen in to our radio broadcast.

2. To eavesdrop; to listen secretly.

   You should close the door for conversations like that. You never know who might be listening in.

• (to listen without participating): listen, sit in
• (to eavesdrop): eavesdrop, overhear

• Leninist