Webster Dictionary(0.00 / 0 votes)Rate this definition: 1  Belligerent. waging war; carrying on war. 2  Belligerent. pertaining, or tending, to war; of or relating to belligerents; as, a belligerent tone; belligerent rights. 3  Belligerent(noun) a nation or state recognized as carrying on war; a person engaged in warfare.