Real Dictionary

wiretap
verb: If someone wiretaps your phone, they attach a special device to the line so that they can secretly listen to your conversations.

wiretap in American English
of or relating to wiretapping
the act or an instance of wiretapping
to tap (a telephone wire, etc.) to get information secretly or underhandedly
adjective: pertaining to or obtained by wiretap
intransitive verb: to tap telephone or telegraph wires for evidence, information, etc
noun: an act or instance of tapping telephone or telegraph wires for evidence or other information
transitive verb: to obtain (information, evidence, etc.) by tapping telephone or telegraph wires

wiretap in British English
verb: to make a connection to a telegraph or telephone wire in order to obtain information secretly