signal

Be a signal for or a symptom of.

“The economic indicators signal that the euro is undervalued”

Communicate silently and non-verbally by signals or signs.

“The diner signaled the waiters to bring the menu”

Any nonverbal action or gesture that encodes a message.

“signals from the boat suddenly stopped”

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

Any incitement to action.

“he awaited the signal to start”

“the victory was a signal for wild celebration”

Notably out of the ordinary.

“the year saw one signal triumph for the Labour party”