English dictionary, thesaurus, translations & etymology
FreeDict.com
Login Flashcards
noun

semaphore

SEM-uh-for
Quiz me More like this

Semaphore (noun) means Equipment used to send visual signals, such as flags, lights, or moving arms, that stand for letters or words. Example: “The old railway signal box still had a working semaphore.”

noun
1
Equipment used to send visual signals, such as flags, lights, or moving arms, that stand for letters or words.
"The old railway signal box still had a working semaphore."
"Ships once used a semaphore to send messages between vessels."
"The semaphore's arms swung down to warn the approaching train."
2
A system of sending messages by holding two flags in set positions, one in each hand, to spell out letters and numbers.
"Scouts are often taught semaphore as part of their training."
"She spelled out the word in semaphore across the beach."
"The sailors communicated by semaphore when radios failed."
3
technical In computing, a mechanism that controls access to a shared resource so that only one process can use it at a time.
"The program uses a semaphore to stop two threads writing to the file at once."
"Each process must acquire the semaphore before entering the critical section."
"Releasing the semaphore lets the next waiting process run."

How to use semaphore

Learner’s notes

In plain EnglishA way of signaling with flags, lights or arm positions, or a computing tool that manages shared access.

When to use it

The computing sense is technical and mainly used by programmers.

Memory tip

Picture a sailor holding two flags in different positions to spell out a letter.

Trace the full origin ↓
Common pairings
flag semaphore semaphore signal use a semaphore semaphore flags
Vocabulary Flow
Build your vocabulary from words like semaphore.
Vocabulary Flow serves the next word, and the next — meaning, pronunciation and an example each time. Practice at your level, or learn English in your own language.
Start vocabulary practice
Test yourself on “semaphore” A quick quiz — meaning, synonyms & usage →

Fill the gap

Can you complete this real example?

The old railway signal box still had a working _____.

Etymology

Semaphore was borrowed from French sémaphore, itself built from the Ancient Greek sêma, meaning a sign or mark, joined to a Greek-derived ending meaning a bearer or carrier. The verb was formed later from the noun.

Origin: French (from Ancient Greek)

Rhymes for semaphore

ore bore tore yore lore more core fore sore gore pore amore
See all rhymes for semaphore →

Frequently asked questions

What is semaphore in simple terms?
It is a way of sending messages using visual signals, such as flags or moving arms, instead of words or sound.
What does semaphore mean in computer science?
It refers to a mechanism that manages access to a shared resource so that only one process uses it at a time, avoiding conflicts.
Where does the word semaphore come from?
It comes from French sémaphore, built from Greek roots meaning sign and carrier.
What is the meaning of semaphore?
"semaphore" (noun) means equipment used to send visual signals, such as flags, lights, or moving arms, that stand for letters or words.