firewall

American  

[fahyuhr-wawl] / ˈfaɪərˌwɔl /

Or fire wall

noun

1. a partition made of fireproof material to prevent the spread of a fire from one part of a building or ship to another or to isolate an engine compartment, as on a plane, automobile, etc.

2. a person, thing, or event that acts as a barrier or protection against something undesirable.

   The new employee handbook should create a firewall against unethical business conduct.

3. Digital Technology. an integrated collection of security measures designed to prevent unauthorized electronic access to a networked computer system.

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firewall British  

noun

1. a fireproof wall or partition used to impede the progress of a fire, as from one room or compartment to another

2. computing a computer system that isolates another computer from the internet in order to prevent unauthorized access

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firewall Scientific  

/ fîr′wôl′ /

1. A software program or hardware device that restricts communication between a private network or computer system and outside networks.

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firewall Cultural  

1. A means of separating a computer network from outside networks for security purposes. A server outside an organization's own network may be used to funnel all incoming and outgoing traffic to assist in keeping out viruses, as well as to prevent unauthorized outsiders from gaining access to a network.

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Etymology

Origin of firewall

An Americanism dating back to 1750–60

Explanation

A sturdy barrier that's flame resistant is called a firewall. Another kind of firewall is the one a computer system uses to block potentially dangerous external networks or hackers. The original firewall was exactly what it sounds like: a wall that provides a safe barrier against fire. These firewalls are often used in large buildings (or between structures that are connected) to prevent a fire from spreading once it's started. The term was borrowed to describe something in computing that plays a similar role, limiting the access to a network, usually from the internet. Your firewall helps protect your computer against viruses and malware.

Example Sentences

Meanwhile, Morgan Stanley analyst Meta Marshall wrote of “continued momentum and firewall share gains” that may have driven Palo Alto Networks’ revenue above the 17% to 18% growth rate that the company had projected.

From MarketWatch • Feb. 17, 2026

The built-in R.O.B.E.R.T. firewall blocks ads, trackers, and malware before they reach you.

From Salon • Feb. 12, 2026

But Rockwell’s time traveler — he really is one — is used to a firewall of resistance.

From Los Angeles Times • Feb. 12, 2026

Today, there is a strict firewall between the government and the people tasked with selecting the Nobel laureate.

From The Wall Street Journal • Jan. 31, 2026

I torched through the firewall, maybe five seconds.

From "Burning Blue" by Paul Griffin