noun. A means of conveying information as an alternate to a regular avenue of communication, especially in government and diplomacy.

noun. A usually subconscious utterance or gesture made by a listener in a conversation indicating that the listener is paying attention or understands what is being said.

verb. To employ a back channel.

verb. To employ non-verbal (oral and visual) means to influence a speaker without interruption.

noun. A real-time online discussion that occurs simultaneously with a verbal presentation.