A belligerent (lat. bellum gerere, "to wage war") is an individual, group, country or other entity which acts in a hostile manner, such as engaging in combat. Belligerent comes from Latin, literally meaning "They (should) wage war." Unlike the colloquial use of belligerent to mean aggressive, its formal use does not necessarily imply that the belligerent country is an aggressor.
In times of war, belligerent countries can be contrasted with neutral countries and non-belligerents. However, the application of the laws of war to neutral countries and the responsibilities of belligerents are not affected by any distinction between neutral countries, neutral powers or non-belligerents. A non-belligerent may nevertheless risk being considered a belligerent if it aids or supports a belligerent in a way proscribed by neutral countries.
An interesting use of the term arose during the American Civil War, when the Confederate States of America, though not recognized as a sovereign state, was recognized as a belligerent power, and thus Confederate warships were given the same rights as United States warships in foreign ports.
Read more about Belligerent: Belligerency