signal noun [C]
› an action, movement, or sound that gives information, a message, a warning, or an order: I tried to call but kept getting a busy signal. When the lieutenant gave the signal, five police officers charged into the apartment. In retrospect, looking at how she was acting, we should have been able to recognize the danger signals.› A signal is also a device, often with lights, that shows people or vehicles whether to stop, go, or move carefully.
› to show that something is going to happen or that you are going to do something: Drops in sales signal a tough year ahead.signal that It recently signalled that it would not stand in the way of a takeover bid.