"Go berserk" is an idiom that means to become uncontrollably angry or out of control. There are numerous synonyms to express the same, a few are - freak out, lose it, fly off the handle, blow a fuse, go nuts, flip out, go ballistic, go haywire, go wild, lose one's cool, and so on. These synonyms are commonly used to indicate an individual's sudden and unpredictable behavior when provoked. Whether it's in response to a disagreement or any other trigger, these terms represent an individual's drastic mindset shift from being rational to losing one's composure. So, the next time someone goes berserk, one can resort to using these synonyms to describe their behavior distinctly.