berserko

chiefly US, informal

1. 1 :  highly excited or agitated :  frenzied berserk A berserko crowd of 73,614 tromped through the snow outside Mile High Stadium and painted the place orange for the long-awaited event. — Chris Jenkins, San Diego Union-Tribune, 30 Sept. 1985 … most dogs will go berserko at the very thought of riding shotgun with the fresh, free wind in their hair, ears flapping and life without care. — Rick Methot, Lebanon (Pennsylvania) Daily News, 26 Aug. 2012

2. 2 :  unusual or bizarre often in a way that suggests or reflects insanity :  crazy But berserko plots are what we expect from the TV soaps, and what we deserve if we watch them. — John Leonard, New York Magazine, 10 June 1996 … Jack Nicholson's berserko performance as Jack Torrance, an alcoholic playwright and interim hotel caretaker who seemed bent on murdering his desperate wife and telepathic son even before the opening credits had finished rolling. — John Leonard, New York Magazine, 28 Apr. 1997