If you listen in to a private conversation, you secretly listen to it.
He assigned federal agents to listen in on Martin Luther King’s phone calls.
= eavesdrop
PHRASAL VERB : V P to/on n , also V P
If you listen in to a private conversation, you secretly listen to it.
He assigned federal agents to listen in on Martin Luther King’s phone calls.
= eavesdrop
PHRASAL VERB : V P to/on n , also V P
Collins COBUILD Advanced Learner's English Dictionary. Английский словарь Коллинз COBUILD для изучающих язык на продвинутом уровне. 2006