Webster's Revised Unabridged Dictionary · 1913

Berserk

Berserk ({not transcribed}) , noun

[Icelandic berserkr.]

1.
(Scand. Mythology) One of a class of legendary heroes, who fought frenzied by intoxicating liquors, and naked, regardless of wounds. — Longfellow
2.
One who fights as if frenzied, like a Berserker.

Also: Berserker

Berserk (bẽr*sẽrk"; bẽr*zẽrk"; bẽr"sẽrk) , adjective

[See berserk, n.]

frenzied; crazed; usually in predicate position.