a. An indicator, such as a gesture or colored light, that serves as a means of communication. See Synonyms at gesture.
b. A message communicated by such means.
2. Something that incites action: The peace treaty was the 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
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"
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
make synchronous and adjust in time or manner; "Let's synchronize our efforts"
proper alignment; the property possessed by something that is in correct or proper alignment; "out of true"
make level, square, balanced, or concentric; "true up the cylinder of an engine"