ὠτακουστής

οῦ, ὁ
A. listener, eavesdropper, of a person employed as a spy by tyrants, Arist. Pol. 1313b14, Mu. 398a21, Plb. 16.37.1, Plu. 2.522f.
Liddell, Scott & Jones
A Greek-English Lexicon, 1940
An open-access project