|1.||cone of silence|
An imaginary zone from which sound or discussion can't escape. The cone of silence is used to keep something quiet or private. Most often applied to spoken communication, but can also apply to writing or email.
From a running gag on the TV show "Get Smart" in which a plexiglass device would lower from the ceiling and cover the heads of two speakers, so that their conversation couldn't be spied upon. The cone of silence rarely worked correctly on TV, and usually isn't much better in real life.
Employee 1: Hey, I just overheard your boss talking about you. You won't believe what he said.
Employee 2: Let's take this one to the cone of silence.