Definition of "warning"

Although the Celebrity was almost impervious to sarcasm, he was now beginning to exhibit visible signs of uneasiness, […] . It was with a palpable relief that he heard the first warning notes of the figure.

1897 December (indicated as 1898), Winston Churchill, chapter V, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.

“ […] Churchill, my dear fellow, we have such greedy sharks, and wolves in lamb's clothing. Oh, dear, there's so much to tell you, so many warnings to give you, but all that must be postponed for the moment.”

1918, W[illiam] B[abington] Maxwell, chapter VII, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company

Without much warning, a deep voice addressed the crowd, calling for a reverent silence as the Texans who died at the Alamo battle were named.

2008, Laura Hernández-Ehrisman, “Conclusion”, in Inventing the Fiesta City: Heritage and Carnival in San Antonio, University of New Mexico Press, page 194

Risk is everywhere. From tabloid headlines insisting that coffee causes cancer (yesterday, of course, it cured it) to stern government warnings about alcohol and driving, the world is teeming with goblins.

2013 June 22, “Snakes and ladders”, in The Economist, volume 407, number 8841, page 76