smoke signal

1.
historicalglobalneutral
- A column or cloud of smoke produced intentionally as a means of long-distance visual communication, typically to send a prearranged message or call for help.
- A method of signaling used historically by various cultures, notably Indigenous peoples, to convey messages across distance.
2.
globalinformalcolloquial
- A figurative sign or indication intended to attract attention or convey a message; a signal that something requires notice.
- A request or signal for assistance; an action intended to alert others that help or intervention is needed.

Examples: