lunch lid
n. A moratorium, established by the White House, on newsworthy announcements and events during journalists' lunch break.
Financial wires rushed the story out even before the briefing finished, and it apparently caused some heat at the Federal Reserve, although Fed officials would provide no details.

Within an hour, Miss Myers issued a clarification during the so-called "lunch lid," when news conferences and statements are suspended so White House reporters can eat their sandwiches in peace.
—Anne Veigle, “White House gets word on Fed quotes,” The Washington Times, June 11, 1993
1977 (earliest)
During the lunch hour one day the President decided on the spur of the moment that he wanted to have a news picture taken in his office. But the Press Office had declared a lunch "lid" and no photographers were around.
—Frank Cormier, LBJ The Way He Was, Doubleday, January 01, 1977
When White House staffers announce that "the lunch lid is on," correspondents know they can leave the press room and not be in danger of missing something important.