American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

1. One that is violent, upset, or unrestrained.

3. Informal Unrestrained, as with enthusiasm or appetite; wild: berserk over chocolates.

2. Mentally or emotionally upset; deranged: berserk with grief.

a berserk worker who started smashing all the windows.

1. Destructively or frenetically violent: a berserk worker who started smashing all the windows.

(Norse Myth & Legend) Also called: berserker a member of a class of ancient Norse warriors who worked themselves into a frenzy before battle and fought with insane fury and courage

frenziedly violent or destructive (esp in the phrase go berserk )

ber•serk

(bərˈsɜrk, -ˈzɜrk)

1. violently or destructively frenzied: to go berserk.

2. (sometimes cap.) Also, ber•serk′er. a devotee of Odin in early Norse society who fought with frenzied rage in battle.

[1865–70; < Old Norse berserkr]

ber•serk′ly, adv.

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