A soldier, a combatant.
"The militant led his squad through the narrow alleyways to secure the perimeter before dawn."
showing a fighting disposition
"highly competitive sales representative"
"militant in fighting for better wages for workers"
"his self-assertive and ubiquitous energy"
Fighting or disposed to fight; belligerent, warlike.
"The militant protesters blocked the highway, shouting slogans and refusing to disperse until their demands were met."