Unofficial means of communication

• Unofficial means of communication, and a hint to each set of circled letters
• Covert means of communication ... or what's hiding in the circled letters?

Wikipedia Word definitions in Wikipedia
A backchannel is a real-time online conversation using networked computers that takes place alongside live spoken remarks. Backchannel may also refer to: Return channel , a low-speed, or less-than-optimal, telecommunications transmission channel in the ...

Wiktionary Word definitions in Wiktionary
alt. 1 To employ a back channel. 2 (context linguistics English) To employ non-verbal (oral and visual) means to influence a speaker without interruption. n. (context computing English) A real-time online discussion that occurs simultaneously with a verbal ...