Open main menu


English Wikipedia has an article on:
The semaphore signalling alphabet


Borrowed in 1816 from French sémaphore, coined in French from Ancient Greek σῆμα (sêma, sign), and -φορος (-phoros, bearing, bearer), from φέρω (phérō, to bear, carry).


  • (UK) IPA(key): /ˈsɛ.mə.fɔː/
  • (file)


semaphore (countable and uncountable, plural semaphores)

  1. Any visual signaling system with flags, lights, or mechanically moving arms.
    • 2008, Gene Weingarten, Old Dogs: Are the Best Dogs, Simon & Schuster, page 4 [1]:
      Consider the wagging tail, the most basic semaphore in dog/human communication.
  2. 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.
  3. (computing) 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.

Derived termsEdit



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

  1. (transitive, intransitive) To signal using (or as if using) a semaphore.
    • 1990, Peter Hopkirk, The Great Game, Folio Society 2010, p. 425:
      Minutes later, unseen by the defenders, he semaphored back across the valley that he was going to make a fresh attempt.