convey information or instructions by means of a gesture, action, or sound
hold your fire until I signal
a gesture, action, or sound that is used to convey information or instructions, typically by prearrangement between the parties concerned
the firing of the gun was the signal for a chain of beacons to be lit
the policeman raised his hand as a signal to stop
an electrical impulse or radio wave transmitted or received
equipment for receiving TV signals
an apparatus on a railway, typically a coloured light or a semaphore, giving indications to train drivers of whether or not the line is clear
the driver of the mail train overran a signal at danger and ran into the rear of an express