Definition of "firewall" []

• A fireproof wall used as a barrier to prevent the spread of fire. (noun)
• Computer Science Any of a number of security schemes that prevent unauthorized users from gaining access to a computer network or that monitor transfers of information to and from the network. (noun)
• Slang To apply maximum acceleration or thrust. Used of motor vehicles or aircraft. (verb-intransitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "If you have been using the Internet for any length of time, and especially if you work at a larger company and browse the Web while you are at work, you have probably heard the term firewall used."
• "Every day we continue to be fat, dumb, and happy with our IANA private ranges and doing port address translation at the firewall is another day further ensconced in the inebriation of IPv4."
• "We probably need more than that, but a firewall is at least a first step."