Yes, firewall is a Scrabble word!

Noun

1. (colloquial) the application of maximum thrust

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