semaphore

Syllables: se·ma·phore/ˈsɛm.əˌfɔː/US/ˈsɛm.əˌfoɹ/

semaphore noun: any equipment used for visual signalling by means of flags, lights, or mechanically moving arms, which are used to represent letters of the alphabet, or words.

Noun

semaphore (countable and uncountable, plural semaphores)

Any equipment used for visual signalling by means of flags, lights, or mechanically moving arms, which are used to represent letters of the alphabet, or words.
- We must here take the liberty of expostulating with Sir Home [Riggs] Popham and the first Lord of the Admiralty, for having given to the telegraphic machine, invented by that gallant officer, the barbarous name of Semaphore, instead of Sematophore or Semophore—either of them ugly enough.[1820 January, “Art. II.—Thesaurus Græcæ Linguæ ab H. Stephano [Henry Stephens] constructus. Editio nova, auctior et emendatior. Vol. I. Partes I–IV. Londini, in ædibus Valpianis, 1815–1818. [book...
- The large Silver Medal of the Society was this Session voted to Nic[h]olas Harris Nicolas, Esq. of the Inner Temple, for an Improvement on the Vertical Semaphore, and for his method of adapting a shifting Key to Telegraphic Communications, for the purpose of insuring their Secrecy. A Model of Mr....1821, “[Papers in Mechanics.] No. V. Improved Semaphore.”, in Transactions of the Society, Instituted at London, for the Encouragement of Arts, Manufactures, and Commerce; […], volume XXXIX, London...
A visual system for transmitting information using the above equipment; especially, by means of two flags held one in each hand, using an alphabetic and numeric code based on the position of the signaller's arms; flag semaphore.
- Its [the article's] object is to furnish a rule for determining the number of distinct signals which can be made by any semaphore, whatever be the number of arms or indicators, of whatever be the number of positions of each arm. In the Cyclopædia of Rees, the number of signals which the semaphores...1834 October, Charles Blackburn, “XXXV. A Method of Determining the Number of Signals which Can be Made by the Modern Telegraphs.”, in David Brewster, Richard Taylor, Richard Phillips, editors, The...
- Buried treasures are naturally among the problems which have come to Mr. [Sherlock] Holmes. One genuine case was accompanied by a diagram here reproduced. [...] Each Indiaman in those days had its own semaphore code, and it is conjectured that the three marks upon the left are signals from a...1924 September, Arthur Conan Doyle, “Sidelights on Sherlock Holmes”, in Memories and Adventures, Boston, Mass.: Little, Brown, and Company, →OCLC, page 110
A bit, token, fragment of code, or some other mechanism which is used to restrict access to a shared function or device to a single process at a time, or to synchronize and coordinate events in different processes.
- The thread increments the semaphore to prevent other threads from entering the critical section at the same time.
- Several synchronization techniques have been proposed and many of them have been adopted by parallel and distributed operating systems or parallel programming platforms. [...] Semaphores represent another synchronization technique that is mainly used by traditional stand-alone operating systems.1996, P. Theodoropoulos, G. Manis, P. Tsanakas, G. Papakonstantinou, “Extending Synchronization PVM Mechanisms”, in Arndt Bode, Jack Dongarra, Thomas Ludwig, Vaidy Sunderam, editors, Parallel Virtual...

Verb

semaphore (third-person singular simple present semaphores, present participle semaphoring, simple past and past participle semaphored)

(ambitransitive, figuratively) To signal using, or as if using, a semaphore, with the implication that it is done nonverbally.
- The person intending to Semaphore will make the International Code Signal VOX (I am going to Semaphore to you), and set his Semaphore at the alphabetical sign [...] with the Indicator out, and wait until the person to whom the Semaphore signal is to be made hoists his answering pennant close up....1907, United States Hydrographic Office, “Distant Signals”, in International Code of Signals, American edition, Washington, D.C.: Government Printing Office, →OCLC, part III, page 539
- These gunny-sack chaps are not animals or savages. Look, Henry! They are semaphoring! See that tree there, and that big one across the cañon. Watch the branches wave.1920 September, Jack London, chapter X, in Hearts of Three, New York, N.Y.: The Macmillan Company, →OCLC, page 137

semaphore meaning in Tamil and Kannada

Examples of semaphore in a sentence

N's Semaphore has been placed in the Repository of the Society.1821, “[Papers in Mechanics.] No. V. Improved Semaphore.”, in Transactions of the Society, Instituted at London, for the Encouragement of...
The arms of the semaphore at the settlement were, in fact, gesticulating with comical vehemence.1875, Marcus Clarke, “Running the Gauntlet”, in His Natural Life [For the Term of His Natural Life], volume III, London: Richard Bentley...
And so they went down, Jim steering by his father, turn for turn, over the Mayapur Bar, with the semaphores on each bank duly signalling the depth of water, [...]1895 January–June, Rudyard Kipling, “An Unqualified Pilot”, in Land & Sea Tales for Scouts and Guides, Bombay: The Gresham Publishing...
It is essentially an emergency device, primarily for use on single track railroads, and is intended to place the control of semaphores at the several stations under the control of the dispatcher.1906 July 19, “The Wright Telegraph Railroad Signal”, in The Iron Age, volume LXXVIII, New York, N.Y.: David Williams Company […], →OCLC...

All 16 example sentences with semaphore

Forms of semaphore

Noun
plural	semaphores
Verb
third-person singular present	semaphores
present participle	semaphoring
past participle	semaphored
past	semaphored

Plural of semaphore: semaphores

Origin of semaphore

The noun is borrowed from French sémaphore, from Ancient Greek σῆμα (sêma, “mark, sign, token”) + French -phore (from Ancient Greek -φόρος (-phóros, suffix indicating a bearer or carrier)). By surface analysis, sema- + -phore. The verb is derived from the noun.

Words formed from semaphore

Phrases with semaphore

Questions about semaphore

What does semaphore mean?: Semaphore means any equipment used for visual signalling by means of flags, lights, or mechanically moving arms, which are used to represent letters of the alphabet, or words.
What is semaphore in Tamil?: Semaphore in Tamil is அணுகல் குறியீடு. See Semaphore meaning in Tamil.
How do you use semaphore in a sentence?: N's Semaphore has been placed in the Repository of the Society.
What part of speech is semaphore?: Semaphore can be a noun or a verb.
How do you pronounce semaphore?: Semaphore is pronounced /ˈsɛm.əˌfɔː/ (UK).
What is the plural of semaphore?: The plural of semaphore is semaphores.

Words near semaphore in the dictionary

Adapted from Wiktionary: semaphore (page history and authors); semaphore (Tamil Wiktionary) (page history and authors); semaphore (Kannada Wiktionary) (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

Pronunciation audio from Wikimedia Commons, each file under its own free license: En-uk-semaphore.oga.

Cite this entry: “semaphore.” Word.ws, https://word.ws/semaphore. Based on Wiktionary, CC BY-SA 4.0.