Noun

• S: (n) signal, signaling, sign (any nonverbal action or gesture that encodes a message) "signals from the boat suddenly stopped"
• S: (n) signal (any incitement to action) "he awaited the signal to start"; "the victory was a signal for wild celebration"
• S: (n) signal (an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes)

Verb

• S: (v) sign, signal, signalize, signalise (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"
• direct troponym / full troponym
• direct hypernym / inherited hypernym / sister term
• derivationally related form
• sentence frame
• S: (v) bespeak, betoken, indicate, point, signal (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"

Adjective

• S: (adj) signal (notably out of the ordinary) "the year saw one signal triumph for the Labour party"