Stop press

High-volume newspaper printing press.

"Stop (the) Press(es)" is a phrase stemming from the printed news media as an exclamation signifying the discovery of the need to change the content of an issue just before, or during its printing

Since this meant that the printing press literally had to be stopped or delayed and much of the existing copies of a publication which had already printed had to be discarded - which carried extreme cost, it is a phrase indicating the arrival of extremely significant news or the discovery of an extremely grave error. The phrase is common in an idiomatic context, referring to the discovery of significant information - perhaps most frequently used ironically .