signal

any nonverbal action or gesture that encodes a message; "signals from the boat suddenly stopped"

any incitement to action; "he awaited the signal to start"; "the victory was a signal for wild celebration"

an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

communicate silently and non-verbally by signals or signs; "He signed his disapproval with a dismissive hand gesture"; "The diner signaled the waiters to bring the menu"

be a signal for or a symptom of; "These symptoms indicate a serious illness"; "Her behavior points to a severe neurosis"; "The economic indicators signal that the euro is undervalued"

notably out of the ordinary; "the year saw one signal triumph for the Labour party"