from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A visual signaling apparatus with flags, lights, or mechanically moving arms, as one used on a railroad.
  • n. A visual system for sending information by means of two flags that are held one in each hand, using an alphabetic code based on the position of the signaler's arms.
  • transitive v. To send (a message) or to signal by semaphore.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Any visual signaling system with flags, lights, or mechanically moving arms.
  • n. A visual system for transmitting information by means of two flags that are held one in each hand, using an alphabetic and numeric code based on the position of the signaler’s arms.
  • n. 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.
  • v. To signal using (or as if using) a semaphore.

from the GNU version of the Collaborative International Dictionary of English

  • n. A signal telegraph; an apparatus for giving signals by the disposition of lanterns, flags, oscillating arms, etc.

from The Century Dictionary and Cyclopedia

  • To signal with a semaphore; humorously, wave one's arms and signal like a semaphore.
  • n. A mechanical device for displaying signals by means of which information is conveyed to a distant point.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • v. send signals by or as if by semaphore
  • v. convey by semaphore, of information
  • n. an apparatus for visual signaling with lights or mechanically moving arms


Greek sēma, sign + -phore.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Borrowed in 1816 from French sémaphore, coined in French from Ancient Greek σῆμα (sêma, "sign"), and -φωρος (-phoros), from φέρω (férō, "to bear, carry"). (Wiktionary)


  • The semaphore is a quicker means of communication than the wig wag; but the wig wag can be used in a prone position under shelter.

    Military Instructors Manual

  • Between ships and the land there are used what are called semaphore signals, which are made by means of a mast provided with three arms and a disk placed at the upper part.

    Scientific American Supplement, No. 508, September 26, 1885

  • The semaphore is a machine with two arms which may be moved into various positions to make letters.

    Scouting For Girls, Official Handbook of the Girl Scouts

  • The telegraph station at the semaphore was a little, square, stone hut, roofed with slate, perched high on the cliffs.

    The Maids of Paradise

  • And then Edward, who by this point was in danger of complete mental disintegration, descended further, into a form of anti-language that Sugar called "semaphore". - Telegraph online, Daily Telegraph and Sunday Telegraph

  • Basically a semaphore is a counter (integer) that allows a thread to get into

    Javalobby - The heart of the Java developer community

  • Slide 17: Semaphores • Dijkstra - 1965 • A semaphore is a data structure consisting of a counter and a queue for storing task descriptors • Semaphores can be used to implement guards on the code that accesses shared data structures • Semaphores have only two operations, wait and release (originally called P and V by Dijkstra) • Semaphores can be used to provide both competition and cooperation synchronization Copyright © 2007 Addison-Wesley.

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  • Her purring flashed on and off like the lights on top of radio towers, a kind of semaphore rumble.



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