[ber.serk] or ber.serk.er n [ON berserkr, fr. bjorn bear + serkr shirt] (1818) 1: an ancient Scandinavian warrior frenzied in battle and held to be invulnerable
2: one whose actions are recklessly defiant
[2]berserk adj (1851): frenzied, crazed--usu. used in the phrase go berserk "sinister ravings of an imagination gone ~ --John Gruen" -- berserk adv -- ber.serk.ly adv