eavesdrop

To hear (intentionally) a conversation one is not intended to hear; to listen in.

I hope nobody was eavesdropping on our conversation last night, since it got so personal.

To listen for another organism's calls, so as to exploit them.

[…] Eastern Red Bat will eavesdrop on the sonar calls of other red bats to locate potential insect prey.

Frog-biting midges also depend on eavesdropping for reproduction, and one would predict similarly strong selection to evolve auditory adaptations for hearing and localizing calls of their hosts.

The dripping of rain from the eaves of a house.

The space around a house on which such water drips.

A concealed aperture through which an occupant of a building can surreptitiously listen to people talking at an entrance to the building.

The act of intentionally hearing a conversation not intended to be heard.

Were you having a little eavesdrop on us last night?