sig·nal¹ / ˈsignəl/ • n. 1. 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 indication of a state of affairs: the markets are waiting for a clear signal about the direction of policy. ∎  an event or statement that provides the impulse or occasion for something specified to happen: the champion's announcement that he was retiring was the signal for scores of journalists to gather at his last match. ∎  an apparatus on a railroad, typically a colored light or a semaphore, giving indications to train engineers of whether or not the line is clear. ∎  Bridge a prearranged convention of bidding or play intended to convey information to one's partner.2. an electrical impulse or radio wave transmitted or received: equipment for receiving TV signals.• v. (-naled, -nal·ing; chiefly Brit. -nalled, -nal·ling) [intr.] transmit information or instructions by means of a gesture, action, or sound: hold your fire until I signal. ∎  [tr.] instruct (someone) to do something by means of gestures or signs rather than explicit orders: she signaled Charlotte to be silent. ∎  (of a cyclist, motorist, or vehicle) indicate an intention to turn in a specified direction using an extended arm or flashing indicator: Stone signaled right | the truck signaled to turn left. ∎  [tr.] indicate the existence or occurrence of (something) by actions or sounds: they could signal displeasure by refusing to cooperate. ∎  give an indication of a state of affairs: she gave a glance that signaled that her father was being secretive.DERIVATIVES: sig·nal·er n.sig·nal² • adj. striking in extent, seriousness, or importance; outstanding: he attacked the administration for its signal failure of leadership.DERIVATIVES: sig·nal·ly adv.

signal
1. A form of data that is usually envisaged as a sequence of values of a scalar quantity – the amplitude – recorded (i.e. measured, tabulated, or plotted) against time. The amplitude is most often, but by no means always, an electric potential. For example, if the signal is a sine wave with a mean value of zero (symmetrical about zero volts), then the amplitude is the value of the peak voltage. See also discrete and continuous systems, space domain.

2. Any path transmitting some data or function. See also control signal.

3. To convey data or control information from one point to another.