It’s an adjective and it means having or showing a bad temper; being annoyed and irritable; being cranky or disagreeable. You know the sort of person, they come into work pissed off with everything and everybody and just looking for an excuse to blame somebody for everything that is wrong in their crappy lives, the world, the universe. Thoroughly unpleasant shitbags.
fucking emo assholes that team up in mm2 and the one that is murderer kills everyone else but their dumbass team, or they fucking camp the gun until one of their teammates gets the gun because they're too scared to die.