—n. 1. anything that serves to indicate, warn, direct, command, or the like, as a light, a gesture, an act, etc.: a traffic signal; a signal to leave. 2. anything agreed upon or understood as the occasion for concerted action.
3. an act, event, or the like that causes or incites some action: The unjust execution was the signal for revolt. 4. a token; indication.
5. Electronics.an electrical quantity or effect, as current, voltage, or electromagnetic waves, that can be varied in such a way as to convey information.
6. Cards.a play that reveals to one's partner a wish that he or she continue or discontinue the suit led.
—adj. 1. serving as a signal; used in signaling: a signal flag. 2. unusual; notable; outstanding: a signal exploit.
—v.t. 1. to make a signal to.
2. to communicate or make known by a signal.
—v.i. to make communication by a signal or signals.