United Nations, as a world player, has influential role to play in the foreign policy formation of its members and the diplomacy carried out by its regional international organizations. Hence, it is useful to learn about position, actions and ways and means this institution uses in its campaign against the phenomena of terrorism. According to the findings in this research, there are two main orientations in the official and non-official views of member nations in the definition of the concept of terrorism. First definitional orientation, which is also prevailing one, and is posed by western scholars, tries to classify any violent movement against the political systems of western nations as acts of terrorism and therefore unacceptable irrespective of their underlying causes, motivations, and beliefs. The second definitional orientation, in contrast, differentiates independent movements, struggle against foreign occupation and racial discrimination from that of terrorist movements. This latter position is assumed mainly by southern nations in general and by the members of Islamic Conference Organization in particular.