In cybersecurity, 'WAF' stands for Web Application Firewall. A WAF acts as a barrier between a web application and the internet, monitoring and filtering HTTP traffic. It helps protect web applications from common attacks such as SQL injection, cross-site scripting (XSS), and DDoS attacks. By analyzing incoming requests and enforcing security policies, WAFs prevent unauthorized access and data breaches. They are crucial in maintaining web application integrity and ensuring compliance with security regulations, thereby protecting sensitive user data.