In telecommunication, the term crosstalk (XT) has the following meanings:

1. Undesired capacitive, inductive, or conductive coupling from one circuit, part of a circuit, or channel, to another.

2. Any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

Note: In telephony, crosstalk is usually distinguishable as speech or signaling tones.

Source: from Federal Standard 1037C and from MIL-STD-188