A Quick and Simple Dictionary

firewall

1. Noun.  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. Noun.  (computer security) 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. Noun.  The part of an automobile body that separates the engine from the driver and passengers.
4. Verb.  (transitive, computer security) To protect with a firewall.
5. Verb.  (transitive, computer security) To block with a firewall.
6. Verb.  (intransitive, motor vehicles or aircraft, slang) To use maximum acceleration.