What is a synonym for eavesdropping?

Here are some synonyms for eavesdropping, depending on the specific nuance you want to convey:

Formal:

* Overhearing

* Listening in

* Interception

* Wiretapping (if it involves electronic means)

* Surveillance (if it's part of a larger effort)

Informal:

* Snooping

* Listening at the keyhole

* Bugging

* Peeping

* Nosying

Figurative:

* Catching wind of

* Getting an earful of

* Picking up on

* Overhearing whispers

The best synonym to use will depend on the context of your sentence and the level of formality you want to convey.