Synonyms for Belligerent:

adj.

aggressive (adjective)
combative, warlike, domineering, forward, truculent, offensive, aggressive, assertive, hostile, militant, pushy, determined, bellicose.
all (adjective)
aggressive.
argumentative (adjective)
scrappy.
nasty, argumentative (adjective)
combative, warlike, fighting, hostile, truculent, quarrelsome, aggressive, antagonistic, militant, pugnacious, scrappy, contentious, bellicose.
offensive (adjective)
offensive.

n.

black out, aggressor, air cover, active duty, Beleaguered, battle cry, active service, bombed-out. cross, attack, quarrelsome, mad, upset, angry, put out, annoyed, scrappy, contentious, pugnacious, irritated, fed up, displeased. front line, attitude, military, tactical, militarized, embattled, in the field, paramilitary. soldier, warrior, conflict. belligerent (noun)
fighter, fighting, aggressive, war-ridden, warring, militant, battler, hostile, unpeaceful, scrapper, combatant.
combatant (noun)
battler, warrior.
warlike (noun)
martial, contentious, quarrelsome, pugnacious, antagonistic, full of fight, warmongering.

Other synonyms:

bombed-out, displeased, black out, militarized, annoyed, quarrelsome, active duty, martial, Beleaguered, military, aggressor, fed up, active service, front line, embattled. paramilitary, pugnacious, angry, warrior, air cover, scrappy, irritated, put out, tactical, soldier, mad. upset. contentious. combative
fighting.
Other relevant words:
contentious, antagonistic, conflict, battler, martial, military, scrapper, fighter, upset, militarized, scrappy, war-ridden, Beleaguered, front line, fighting, bombed-out, combatant, attack, attitude, quarrelsome, embattled, soldier, pugnacious, displeased, warring, irritated, full of fight, paramilitary, warrior, annoyed, tactical, aggressor, warmongering, unpeaceful, angry, aggressive, cross, mad.

Usage examples for belligerent

  1. Moreover, the American Government drew up protests and demands for compensation, for use in case of any infringement of these rights, or of any interference with their free exercise on the part of the belligerent Powers. – My Three Years in America by Johann Heinrich Andreas Hermann Albrecht Graf von Bernstorff
  2. Instead of a pledge, therefore, of a suspension of the embargo as to her in case of such a repeal, it was presumed that a sufficient inducement might be found in other considerations, and particularly in the change produced by a compliance with our just demands by one belligerent and a refusal by the other in the relations between the other and the United States. – State of the Union Addresses of Thomas Jefferson by Thomas Jefferson
  3. The armistice was prolonged to March 12th; but it was in the option of either of the belligerent powers to end it after March 3rd by giving three days' notice. – The Franco-German War of 1870-71 by Count Helmuth, von Moltke