signal

American  

[sig-nl] / ˈsɪg nl /

noun

1. anything that serves to indicate, warn, direct, command, or the like, such as a light, a gesture, an act, etc.: a signal to leave.

   a traffic signal;

   a signal to leave.

   Synonyms:

   sign

2. anything agreed upon or understood as the occasion for concerted action.

3. an act, event, or the like that causes or incites some action.

   The unjust execution was the signal for revolt.

4. a token; indication.

   Synonyms:

   sign

5. Electronics. an electrical quantity or effect, as current, voltage, or electromagnetic waves, that can be varied in such a way as to convey information.

6. Cards. a play that reveals to one's partner a wish that they continue or discontinue the suit led.

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adjective

1. serving as a token or indication; used in communiating an intention, warning, or command.

   a signal flag.

2. unusual; notable; outstanding.

   a signal exploit.

   Synonyms:

   striking, remarkable, exceptional, unique

verb (used with object)

signaled, signaling, signalled, signalling

1. to make a token or indication to.

2. to communicate or make known by a token or indication.

verb (used without object)

signaled, signaling, signalled, signalling

1. to make communication by something that serves to indicate, warn, direct, command, or the like.

signal British  

/ ˈsɪɡnəl /

noun

1. any sign, gesture, token, etc, that serves to communicate information

2. anything that acts as an incitement to action

   the rise in prices was a signal for rebellion

3. 1. a variable parameter, such as a current or electromagnetic wave, by which information is conveyed through an electronic circuit, communications system, etc

   2. the information so conveyed

   3. ( as modifier )

      signal strength

      a signal generator

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adjective

1. distinguished or conspicuous

2. used to give or act as a signal

verb

1. to communicate (a message, etc) to (a person)

signal Scientific  

/ sĭg′nəl /

1. A fluctuating quantity or impulse whose variations represent information. The amplitude or frequency of voltage, current, electric field strength, light, and sound can be varied as signals representing information.

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Other Word Forms

• presignal
  noun
• resignal
  verb
• signaler
  noun
• signaller
  noun
• unsignaled
  adjective
• unsignalled
  adjective

Etymology

Origin of signal

First recorded in 1350–1400; Middle English noun from Old French seignal, signal, from Medieval Latin signāle, Late Latin, noun use of neuter of signālis “of a sign”; see sign, -al ², -al ¹

Explanation

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.

Example Sentences

In a separate operation, hackers created a fake Signal account impersonating the EU Ambassador in Armenia Vassilis Maragos, and invited NGO leaders to a fake conference on Armenia-EU relations.

From BBC • May 3, 2026

Signal also goes further than WhatsApp on data privacy, making metadata such as when the message was delivered and its recipient invisible even to the company itself.

From Barron's • Apr. 25, 2026

"The federal government is assuming that the phishing campaign targeting the Signal messaging service was presumably run from Russia," a government source told AFP.

From Barron's • Apr. 25, 2026

Appeared in the April 20, 2026, print edition as 'Bonds, Oil Signal Investor Caution'.

From The Wall Street Journal • Apr. 20, 2026

He joined the Signal Intelligence Service early in the war and mastered the Japanese language in three months in order to join the fight to crack Japan's secret military communications.

From "Spies: The Secret Showdown Between America and Russia" by Marc Favreau

Related Words

• alarm
• beacon
• cue
• gesture
• indicator
• sign