back channel

基本解释

How far do other, similar relationships between military establishments provide a back-channel when conventional diplomacy is not enough?
当传统外交乏力，军方当局之间类似的关系在提供一个后备通道方面，能走多远？
Five other fields in the first auction may be offered again, but not until next year—and only if back-channel talks with unsuccessful bidders come to nothing.
参与第一次开标的其它五处油田可能再次出售，但要等到明年──而只要未投标者经由秘密管道谈判注定失败。
IN SEPTEMBER 1999, when East Timor was burning and Indonesia was angrily accusing Australia of supporting secession there, a diplomatic back-channel quietly opened.
1999年9月，东帝汶一片火海，印度尼西亚愤怒地指责澳大利亚在那支持它的分离，而这时，两国之间一条秘密渠道开通了。

He cites the early involvement of the CEOs, referencing back-channel efforts involving News Corp.
FORBES: A Hollywood Ending?
Have there been any discussions, back-channel phone conversations between the President and any of these Republican leaders?
WHITEHOUSE: Press Briefing
Back-channel sales data from web advertisers indicates pricing has begun heading higher as demand remains strong, he noted in a research note Tuesday.
FORBES: Magazine Article