signal in WordNet English dictionary

1. 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"
   bespeak  betoken  indicate  point  signal 
   
2. 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"
   sign  signal  signalize  signalise 
   

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

1. notably out of the ordinary
   "the year saw one signal triumph for the Labour party"
   signal