smoke signal

plural smoke signals · alternative smoke-signal

1. often pluralizedA method of long-distance communication sometimes used in ancient and undeveloped societies, consisting of messages conveyed by means of columns or intermittent puffs of smoke.
2. A message or sign sent by this method.

   "I have seen the first of the smoke signals, Gulunna," he said, "Chief Bulla's tribes are on their way."

   1944, H. Lorna Bingham, Tuckonie's Warrior Friend, page 33, column 2

   1 more example

   However, there are still signs of the careful study of sources—the smoke-signal which brought Caesar news of the Pompeian escape (279; Caes.3.65.2) and the second fortification inside the camp which Caesar attacked (288; Caes.3.66.4-5).

   1971, A. W. Lintott, “Lucan and the History of the Civil War”, in The Classical Quarterly, volume 21, number 2, page 492

3. idiomaticoften pluralizedAn indirect message or indication, especially concerning a future event.

   By every kind of wigwag and smoke signal in the language of diplomacy, the Administration seemed to be trying last week to tell Chinese Communist Boss Mao Tse-tung that he had nothing to worry about from the U.S.

   1950 September 11, “The Wooing of Mao”, in Time

4. A type of flare or combustion device sometimes used as a distress signal.

   A Huskie helicopter was whirring over the Gulf of Tonkin in search of Cullen when Vietnamese 1st Lieut. Nguyen Van Phu, who ditched his flaming Skyraider near the spot where the U.S. pilot went down, fired a smoke signal to attract its attention.

   1965 March 12, “Operation Rescue”, in Time