Constituting, or serving as, a typical sign or index; especially conspicuous or noteworthy; strikingly uncommon: as, a signal example; a signal failure; signal prosperity.Of high grade or quality; eminent; great; elevated: applied to persons and feelings.Synonyms Conspicuous, extraordinary.n. Sign; token; indication.n. A conventional or intelligible sign designed for information or guidance; an object displayed, a motion made, a light shown, a sound given out, or the like, for direction to or communication with a person or persons (especially at a distance) apprised of or able to recognize its intended meaning: as, to hoist, sound, or make a signal; military and naval signals; a warning signal; a book of signals (see signal-book).n. An inciting action or movement; an exciting cause; an initial impulse: as, this tyrannous act was the signal for insurrection.To mark with a sign.To communicate or make known by a signal or by signals: as, to signal orders; a vessel signals its arrival.To make signals to: as, the vessel signaled the forts.To he a sign or omen.To give a signal or signals; make communication by signals.n. n. In whist, any method of showing that the player wants trumps led. See trumps signal.