[ sig-nl ]
See synonyms for: signalsignaledsignalingsignalled on

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

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

  1. an act, event, or the like that causes or incites some action: The unjust execution was the signal for revolt.

  2. a token; indication.

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

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

  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.

verb (used with object),sig·naled, sig·nal·ing or (especially British) sig·nalled, sig·nal·ling.
  1. to make a token or indication to.

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

verb (used without object),sig·naled, sig·nal·ing or (especially British) sig·nalled, sig·nal·ling.
  1. to make communication by something that serves to indicate, warn, direct, command, or the like.

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, -al2, -al1

Other words for signal

Other words from signal

  • sig·nal·er; especially British sig·nal·ler, noun
  • pre·sig·nal, noun, verb (used with object), pre·sig·naled, pre·sig·nal·ing or (especially British) pre·sig·nalled, pre·sig·nal·ing.
  • re·sig·nal, verb re·sig·naled, re·sig·nal·ing or (especially British) re·sig·nalled, re·sig·nal·ling.
  • un·sig·naled, adjective
  • un·sig·nalled, adjective

Words that may be confused with signal Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use signal in a sentence

  • It was afterwards ascertained that a mistake had been made in reference to the vessel that had signalled.

  • He signalled the porter, who opened one of the big glass doors and signified that the countess could depart.

    The Weight of the Crown | Fred M. White
  • He called to her, he rallied her; he signalled to Thyrsis to help him—to inspire her, to goad her to new endurance.

    Love's Pilgrimage | Upton Sinclair

British Dictionary definitions for signal


/ (ˈsɪɡnəl) /

  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

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

    • the information so conveyed

    • (as modifier): signal strength; a signal generator

  1. distinguished or conspicuous

  2. used to give or act as a signal

verb-nals, -nalling or -nalled or US -nals, -naling or -naled
  1. to communicate (a message, etc) to (a person)

Origin of signal

C16: from Old French seignal, from Medieval Latin signāle, from Latin signum sign

Derived forms of signal

  • signaller or US signaler, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for signal


[ sĭgnəl ]

  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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.