Mute (function)

From Memory Alpha, the free Star Trek reference.

Mute is a function of starship communications in which the audio feeds are disconnected to allow the person transmitting to confer with advisers surreptitiously. In ship-to-ship communications, a commanding officer can either state "mute" to the communications officer or making a gesture indicating mute. (TNG: "The Outrageous Okona", et al.)