firewall.

1. A system that controls network traffic according to rules to reduce unwanted or harmful access.

2. A wall or similar barrier designed to limit the spread of fire between parts of a building or machine.

3. A barrier of rules or arrangements that keeps activities, interests, or information separated.

Use it for

Words that belong together

• a network firewall
• firewall rules

On the page

The firewall blocked the connection without showing whether the message itself was false.

Usage notes

Primary category: sci-fi. Forms: Noun singular firewall; plural firewalls. Related verb forms: firewall, firewalls, firewalled, firewalled, firewalling. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings. Established modern English lexical item. No separate regional spelling or grammatical inflection entry. Writing functions: description, setting. Commonness: moderately common. Third-person singular: firewalls.