listen_in
1. [ verb ] listen quietly, without contributing to the conversation
Related terms: listen
2. [ verb ] listen without the speaker's knowledge
Synonyms: eavesdrop
Examples:

"the jealous man was eavesdropping on his wife's conversations"

Related terms: listen wiretap eavesdropper
Similar spelling:   listen
  listening
  listener
  lightening
  lighten
  liston
  lighten_up
  listing