1. secretly listen to a conversation:"my father eavesdropped on my phone calls"
Word Originearly 17th century: back-formation from eavesdropper (late Middle English)‘a person who listens from under the eaves’, from the obsolete noun eavesdrop ‘the ground on to which water drips from the eaves’, probably from Old Norse upsardropi, from ups ‘eaves’ + dropi ‘a drop’.
Act of secretly listening to the private communications of others
Eavesdropping is the act of secretly or stealthily listening to the private conversation or communications of others without their consent in order to gather information. Wikipedia