When we talk about terrorism, we often assume that others know what we mean and share the same definition. The words “terrorism” and “terrorist” tell us just as much about the person using the terms as it does about who they are describing. The terms and the tactics flow like a thread through history, but a comprehensive definition remains elusive. This talk delves into the difficulties and pitfalls of defining terrorism. By linking social theory and philosophical thought, we can begin to critically examine why a universal definition of terrorism remains just out of reach.