1. 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 for celebration.
3. Electronics An impulse or a fluctuating electric quantity, such as voltage, current, or electric field strength, whose variations represent coded information.
4. The sound, image, or message transmitted or received in telegraphy, telephony, radio, television, or radar.
Visual signal to patrons that these are reserved and not available to everyone.