Angry or agressive: showing a readiness to fight
: fighting a war: engaging in a war
1) He was drunk and belligerent.
2) The coach became quite belligerent and spit at the umpire's face.
Modification of Latin belligerant-, belligerans, present participle of belligerare which means 'to rage war'.
aggressive, argumentative, assaultive, bellicose, warlike, chippy