signal

/ˈsɪg·nəl/ n [C] (ACTION)

Definition

› 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.

(Definition of signal n (ACTION) from the Cambridge Academic Content Dictionary © Cambridge University Press)