The speed of change in the world of cybersecurity is amazing. If you attend a meeting in which cybersecurity is discussed, it can be like listening to a foreign language, leading you to ask what on earth people who use terms like blue team, SASE, fileless malware and quantum cryptography are talking about. This dictionary began life as the reference section at the back of my first book, Cybersecurity for Beginners, and has taken on a life of its own as a highly-regarded source that defines hundreds of the primary cybersecurity terms. It is designed to be a useful companion for anyone who wants to keep up with cybersecurity terms or confound others with their understanding. This fifth edition