A common assumption underwriting much counterterrorism activity is that terrorism, by definition, is necessarily morally wrong. One aim of this paper is to challenge this assumption by defending a novel definition of ‘terrorism’ that makes the morality of terrorism a question to be answered by the application of moral theories to specific terrorist acts, rather than by definitional fiat. After surveying definitions of ‘terrorism’ current in the literature and identifying criteria for a more adequate definition, the paper explicates and defends a novel definition of ‘terrorism’ that can ground serious inquiry into the moral status of specific acts of terrorism.