wiretapping
noun [ U ] uk/ˈwaɪəˌtæp.ɪŋ/ us/ˈwaɪrˌtæp.ɪŋ/
（对电话的）搭线窃听
the action of secretly listening to other people's conversations by connecting a listening device to their phone
If he suspected an employee of dishonesty, he was not above wiretapping. 如果他怀疑某位雇员说谎，他就会搭线窃听他的电话。