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.
–adjective 7. serving as a signal; used in signaling: a signal flag.
8. unusual; notable; outstanding: a signal exploit.
–verb (used with object)
9. to make a signal to.
10. to communicate or make known by a signal.
–verb (used without object)
11. to make communication by a signal or signals.