firewall (n.)

  1. (colloquial) the application of maximum thrust; he moved the throttle to the firewall'

  2. (computing) a security system consisting of a combination of hardware and software that limits the exposure of a computer or computer network to attack from crackers; commonly used on local area networks that are connected to the internet

  3. a fireproof (or fire-resistant) wall designed to prevent the spread of fire through a building or a vehicle

The dictionary is based on the WordNet Electronic Lexical Database.
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