A signal is a gesture or message that people use to communicate with each other. The wave you give a good friend to call her over from across the room and the impulse that transmits your voice through the telephone to your mother are both signals.

In the course of a single day, you probably send and receive thousands of different signals. When you want to cross the street, you wait for the green light — a signal that it's safe to cross. If you're in a relationship and you're not sure whether you like the person you're dating, you could be sending mixed signals — first acting like you're interested, and then acting uninterested. If your date finally gets tired of your mixed signals while you're at a restaurant, you'll need to signal to your server that it's time for the check.

Definitions of signal
  1. noun
    any action or gesture that encodes a message
    signals from the boat suddenly stopped”
    synonyms: sign, signaling
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    a signal that encodes something (e.g., picture or sound) that has been recorded
    number, phone number, telephone number
    the number is used in calling a particular telephone
    start, starting signal
    a signal to begin (as in a race)
    storm signal
    a signal announcing the approach of a storm (particularly a storm of marked violence)
    beam, radio beam
    a signal transmitted along a narrow path; guides airplane pilots in darkness or bad weather
    system of signalling by hand signs used by bookmakers at racetracks
    time signal
    a signal (especially electronic or by radio) indicating the precisely correct time
    a corner of a page turned down to mark your place
    animal communication
    communication between animals (of the same species)
    alarm, alarum, alert, warning signal
    an automatic signal (usually a sound) warning of danger
    distress call, distress signal
    an internationally recognized signal sent out by a ship or plane indicating that help is needed
    all clear
    a signal (usually a siren) that danger is over
    bugle call
    a signal broadcast by the sound of a bugle
    a signal (usually a bell) announcing the start of curfew restrictions
    (military) a signal to begin a withdrawal from a dangerous position
    (military) the beating of a drum as a signal for lowering the flag at sundown
    radiotelegraphic signal, telegraphic signal
    a signal transmitted by telegraphy
    whistle, whistling
    the act of signalling (e.g., summoning) by whistling or blowing a whistle
    high sign
    a silent signal of warning or recognition
    an arbitrary sign (written or printed) that has acquired a conventional significance
    visual signal
    a signal that involves visual communication
    a signal for attracting attention
    electronic signal
    a signal generated by electronic means
    radio beacon
    a characteristic signal emitted by a transmitter used for navigation
    input, input signal
    signal going into an electronic system
    output, output signal
    signal that comes out of an electronic system
    bologram, bolograph
    record or recording made by a bolometer
    the recording (column or paper strip) on which the constituents of a mixture are adsorbed in chromatography
    the recording produced by an oscillograph
    a recording of breathing made with a spirograph
    a small explosive device that is placed on a railroad track and fires when a train runs over it; the sound of the explosion warns the engineer of danger ahead
    stock symbol
    the letters used to identify listed companies on the securities exchanges where they are traded
    accolade, award, honor, honour, laurels
    a tangible symbol signifying approval or distinction
    storm cone
    a canvas cone hoisted to warn of high winds
    brand, mark, stain, stigma
    a symbol of disgrace or infamy
    item, token
    an individual instance of a type of symbol
    all of the tokens of the same symbol
    birdcall, birdsong, call, song
    the characteristic sound produced by a bird
    air alert
    the warning signal that begins a period of preparation for an enemy air attack
    burglar alarm
    a loud warning signal produced by a burglar alarm
    an internationally recognized distress signal in radio code
    an internationally recognized distress signal via radiotelephone (from the French m'aider)
    a bugle call that signals troops to return
    lights-out, taps
    (military) signal to turn the lights out
    reveille, wake-up signal
    (military) signal to wake up
    (military) a bugle call signaling the lowering of the flag at sunset
    a drumbeat or bugle call that signals the military to return to their quarters
    dit, dot
    the shorter of the two telegraphic signals used in Morse code
    dah, dash
    the longer of the two telegraphic signals used in Morse code
    a symbol of inquisitiveness
    number, numeral
    a symbol used to represent a number
    a system of symbols and symbolic representations
    the Hindu phallic symbol of Siva
    pound, pound sign
    a symbol for a unit of currency (especially for the pound sterling in Great Britain)
    printed symbol, written symbol
    a written or printed symbol
    dollar, dollar mark, dollar sign
    a symbol of commercialism or greed
    a graphic symbol consisting of 2 or more letters combined (usually your initials); printed on stationery or embroidered on clothing
    impression, stamp
    a symbol that is the result of printing or engraving
    watch fire
    a fire lighted at night as a signal
    a visual warning signal
    red light, warning light
    a cautionary sign of danger
    flare, flash
    a burst of light used to communicate or illuminate
    flag, signal flag
    a rectangular piece of fabric used as a signalling device
    the cloak as a symbol of authority
    the Crown (or the reigning monarch) as the symbol of the power and authority of a monarchy
    air sock, air-sleeve, drogue, sock, wind cone, wind sleeve, wind sock, windsock
    a truncated cloth cone mounted on a mast; used (e.g., at airports) to show the direction of the wind
    post, stake
    a pole or stake set up to mark something (as the start or end of a race track)
    point of reference, reference, reference point
    an indicator that orients you generally
    blinker, trafficator, turn indicator, turn signal
    a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn
    worn around arm as identification or to indicate mourning
    rocket, skyrocket
    propels bright light high in the sky, or used to propel a lifesaving line or harpoon
    radar echo
    an electronic signal that has been reflected back to the radar antenna; contains information about the location and distance of the reflecting object
    racon, radar beacon
    a device that, on receiving radar signals, transmits coded signals in response to help navigators determine their position
    beacon, beacon fire
    a fire (usually on a hill or tower) that can be seen from a distance
    the output of a computer in printed form
    read-out, readout
    the output of a computer in readable form
    fire alarm
    a shout or bell to warn that fire has broken out
    foghorn, fogsignal
    a loud low warning signal that can be heard by fogbound ships
    a noise made by the driver of an automobile to give warning;
    red flag
    a flag that serves as a warning signal
    a warning signal that is a loud wailing sound
    alarm bell, tocsin
    the sound of an alarm (usually a bell)
    brake light, stoplight
    a red light on the rear of a motor vehicle that signals when the brakes are applied to slow or stop
    barber's pole
    striped pole outside a barbershop
    a rod carried as a symbol
    (computer science) a graphic symbol (usually a simple picture) that denotes a program or a command or a data file or a concept in a graphical user interface
    insignia, mark, marker, marking
    a distinguishing symbol
    a symbol that establishes the identity of the one bearing it
    a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity
    a small, often stylized graphic symbol
    type of:
    something that is communicated by or to or between people or groups
  2. noun
    any incitement to action
    “he awaited the signal to start”
    “the victory was a signal for wild celebration”
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    type of:
    incitation, incitement, provocation
    something that incites or provokes; a means of arousing or stirring to action
  3. noun
    an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes
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    a signal that temporarily stops the execution of a program so that another procedure can be carried out
    type of:
    electrical energy, electricity
    energy made available by the flow of electric charge through a conductor
  4. adjective
    notably out of the ordinary
    “the year saw one signal triumph for the Labour party”
    making a strong or vivid impression
  5. verb
    communicate by means of an action, gesture, or sound
    “The diner signaled the waiters to bring the menu”
    synonyms: sign, signalise, signalize
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    signal by or as if by a flag or light waved according to a code
    send signals by or as if by semaphore
    signal by means of a mirror and the using the sun's rays
    communicate or signal with a flag
    give a signal by whistling
    type of:
    communicate, intercommunicate
    transmit thoughts or feelings
  6. verb
    be a signal for or a symptom of
    “The economic indicators signal that the euro is undervalued”
    synonyms: bespeak, betoken, indicate, point
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    augur, auspicate, betoken, bode, forecast, foreshadow, foretell, omen, portend, predict, prefigure, presage, prognosticate
    indicate by signs
    designate as if by a mark
    to be a menacing indication of something:"The clouds threaten rain"
    indicate by marking trees with blazes
    indicate the dimensions on
    mark with a signpost, as of a path
    distinguish, signalise, signalize
    make conspicuous or noteworthy
    mark with a buoy
    foretell by divine inspiration
    type of:
    let something be known
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