In Morse code it means 'stop keying'; it is also used in amateur radio as 'silent key'.
There is a page by X22 Report titled WE ARE SAFEGUARDED BY A ‘BLACK EYE’, BUCKLE YOUR SEAT BELTS IT’S GOING TO GET ROUGH – EPISODE 2247 - but I don't see any explanation of the title. There was a video on YouTube but it has been removed.
Perhaps this.
