The lack of a universally applicable definition of terrorism has confounded the understanding of terrorism since the term was first coined in 18th Century France. Although a myriad of definitions of terrorism have been advanced over the years, virtually all of these definitions have been crisis-centered, frequently reflecting the political perspectives of those who seek to define it. In this article, we deconstruct these previously used definitions of terrorism in order to reconstruct a definition of terrorism that is consequence-centered, medically relevant, and universally harmonized. A universal medical and public health definition of terrorism will facilitate clinical and scientific research, education, and communication about terrorism-related events or disasters. We propose the following universal medical and public definition of terrorism: The intentional use of violence--real or threatened--against one or more non-combatants and/or those services essential for or protective of their health, resulting in adverse health effects in those immediately affected and their community, ranging from a loss of well-being or security to injury, illness, or death.