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

Experts say Geck’s ruling could signal how other judges — including in upcoming federal court cases — may rule on the Trump administration’s push to restart the pipelines.

From Los Angeles Times • Apr. 20, 2026

In other industries, McKinsey found no clear signal of shifting production.

From The Wall Street Journal • Apr. 18, 2026

"Seeing the effects of the various tests they were running actually modifying what we were seeing from the signal in real time, that was something really special," he said.

From BBC • Apr. 18, 2026

The strength of this signal showed that the sediment last saw daylight between 6,000 and 8,200 years ago.

From Science Daily • Apr. 18, 2026

The radio signal emitted from the collar can be tracked.

From "Camp Panda" by Catherine Thimmesh

Related Words

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