# firewall

> English word · Noun · IPA /ˈfaɪə.wɔəl/ · frequency rank #21,210

## Definitions
1. A fireproof barrier used to prevent the spread of fire between or through buildings, structures, electrical substation transformers, or within an aircraft or vehicle.
2. The software that monitors traffic in and out of a private network or a personal computer and allows or blocks such traffic depending on its perceived threat.
3. A hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at or near the event horizon.
4. An ethical wall; an organizational or legal separation between two entities that might otherwise cause conflicts of interest.
5. An unwritten agreement among major political parties to refuse to govern or cooperate with national conservative and ultranationalist parties.

## Etymology
From fire + wall. Compare West Frisian brânmuorre, Dutch brandmuur, German Brandmauer, Feuermauer, Swedish brandvägg, brandmur, Icelandic eldvegg. The verb sense for using maximum power or acceleration comes from the engine's firewall being the limit of forward movement of the throttle controls on many simpler vehicles; thus, to get the maximum engine output, one would push the throttle levers or pedal all the way to the firewall. The politics sense is a calque of German Brandmauer.

## Easily confused with
- **farewell** (https://plainspell.com/en/vs/farewell-vs-firewall)
- **fireball** (https://plainspell.com/en/vs/fireball-vs-firewall)

## Common misspellings (10)
`ffirewall`, `fierwall`, `fireawll`, `firewal`, `firewlal`, `firewwall`, `firrewall`, `firweall`, `friewall`, `ifrewall`

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/firewall