What is Signalled?

Signalled definition and meaning on Dictionary terms:
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.
anything agreed upon or understood as the occasion for concerted action.

an act, event, or the like that causes or incites some action: The unjust execution was the signal for revolt.
a token; indication.
Electronics. an electrical quantity or effect, as current, voltage, or electromagnetic waves, that can be varied in such a way as to convey information.
Cards. a play that reveals to one’s partner a wish that he or she continue or discontinue the suit led.

serving as a signal; used in signaling: a signal flag.
unusual; notable; outstanding: a signal exploit.

verb (used with object), sig