ears are flapping

(someone's) ears are flapping

Someone is listening, or trying to listen, to the details of a private conversation. Let's finish this conversation in the meeting room in case people's ears are flapping nearby.
See also: ear, flap

ears are flapping

Said when one suspects that a private conversation is being listened to. If ears are flapping now, we should postpone this discussion until a later time, don't you think?
See also: ear, flap
Farlex Dictionary of Idioms.

his, her, etc. ˈears are flapping

(British English, informal) a person is trying to listen to somebody else’s conversation: I think you’d better tell me later when we’re alone — ears are flapping here.
Flap here means to move quickly backwards and forwards.
See also: ear, flap
Farlex Partner Idioms Dictionary
See also:
  • (someone's) ears are flapping
  • flap
  • someone's ears are flapping
  • open a conversation
  • open a conversation (with one)
  • strike up a conversation
  • strike up a conversation (with one)
  • ear hustle
  • ear hustling
  • eavesdrop on (someone or something)