signal

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An indicator, such as a gesture or colored light, that serves as a means of communication. See Synonyms at gesture.
2. n. A message communicated by such means.
3. n. Something that incites action: The peace treaty was the signal for celebration.
4. n. Electronics An impulse or a fluctuating electric quantity, such as voltage, current, or electric field strength, whose variations represent coded information.
5. n. The sound, image, or message transmitted or received in telegraphy, telephony, radio, television, or radar.
6. adj. Notably out of the ordinary: a signal feat; a signal event.
7. v. To make a signal to: I signaled the driver to proceed.
8. v. To relate or make known by signals: They have signaled their willingness to negotiate.
9. v. To make a signal or signals.

Century Dictionary and Cyclopedia

1. Constituting, or serving as, a typical sign or index; especially conspicuous or noteworthy; strikingly uncommon: as, a signal example; a signal failure; signal prosperity.
2. Of high grade or quality; eminent; great; elevated: applied to persons and feelings.
3. Synonyms Conspicuous, extraordinary.
4. n. Sign; token; indication.
5. 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). Occasions for the use of formal signals abound particularly in military operations, navigation, railroading, and telegraphing (especially by means of semaphores); and the methods and devices employed are almost innumerable. See cut under semaphore.
6. n. An inciting action or movement; an exciting cause; an initial impulse: as, this tyrannous act was the signal for insurrection.
7. To mark with a sign.
8. To communicate or make known by a signal or by signals: as, to signal orders; a vessel signals its arrival.
9. To make signals to: as, the vessel signaled the forts.
10. To he a sign or omen.
11. To give a signal or signals; make communication by signals.
12. n. In whist, any method of showing that the player wants trumps led. See trumps signal.

Wiktionary

1. n. An indication given to another person.
2. n. An on-off light, semaphore, or other device used to give an indication to another person.
3. n. TV, internet, etc An electrical or electromagnetic action, normally a voltage that is a function of time that conveys the information of the radio or TV program or of communication with another party.
4. n. Useful information.
5. n. computing, Unix A simple interprocess communication used to notify a process or thread of an occurrence.
6. v. To indicate.
7. adj. Standing above others in rank, importance, or achievement.

GNU Webster's 1913

1. n. A sign made for the purpose of giving notice to a person of some occurence, command, or danger; also, a sign, event, or watchword, which has been agreed upon as the occasion of concerted action.
2. n. A token; an indication; a foreshadowing; a sign.
3. adj. Noticeable; distinguished from what is ordinary; eminent; remarkable; memorable.
4. adj. Of or pertaining to signals, or the use of signals in conveying information.
5. v. To communicate by signals.
6. v. To notify by a signals; to make a signal or signals to.

WordNet 3.0

1. v. be a signal for or a symptom of
2. n. any incitement to action
3. n. an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes
4. adj. notably out of the ordinary
5. v. communicate silently and non-verbally by signals or signs
6. n. any nonverbal action or gesture that encodes a message