Eavesdropper n. : One who stands under the eaves, or near the window or door of a house, to listen; hence, a secret listener.

Example:
Eavesdropper thought thought a tune I was listening to?

Taxonomy
free encyclopedia, eaves, eavesdroppers, occupants, conversations, Great Hall, SIGINT, eavesdrip, HUMINT, search, private conversation, consent, old adage, Origin, visibility, hole, entrance, admission.

Defination from the web:
Eavesdropper) Jump to: navigation, search ... Ancient Anglo-Saxon law punished eavesdroppers, who skulked in the eavesdrip of another's home, with a fine; the eavesdrip was also sometimes called the eavesdrop. ...