"Smoke signals" refers to a way of communication used by Native Americans in which smoke from a fire is used to create specific signals or patterns to convey a message over a long distance. Full definition
If scientists want to convey this information by the way their names are ordered, the method is similar to sending smoke signals, in code, on a dark, windy night. (sciencemag.org)
And she's already hiring employees who can help her scan the horizon for smoke signals. (mastersofscale.com)
Side missions are indicated by smoke signals, if you take to long to get there they will disappear. (mkaugaming.com)