Day-to-day reports in the mass media about the war against terrorism, terrorist acts and preventative war. What is it that indeed characterizes an act as being a terrorist one? As underlined by many authors, there is disagreement on a common definition of terrorism. From a psychosocial perspective, it is important to underline that an ambiguous notion of terrorism may legitimate the ingroup/outgroup differentiation that affects intergroup relations. The aim of this research is to understand what people refer to when they talk about terrorism and to study the influence of different variables on the interpretation of some violent actions such as war or terrorism acts. Our results on a sample of 251 University students confirm that the basic criterion for the evaluation of the actions is founded upon the distinction between military or civilian targets (i.e. target effect). However, some subjects use also a criterion based on the aggressor’s ethnic-cultural identity (i.e. actor effect).