Using a common friend as a secondary way to communicate to your girlfriend/boyfriend the things that are uncomfortable for you discuss directly with your girlfriend/boyfriend.
"Hey Steph! You're my back channel! What does Lisa like as far as engagement rings go?"
by Flacker January 15, 2007
1 more definition
Getting someone's personal contact information so you don't have to communicate with them through a public means.
We were having a conversation on a public web site, but I wanted to backchannel her so we could get more personal.
by Biggety Big September 17, 2006