Dictionary:

shakeup

  (shāk'ŭp')

A thorough, often drastic reorganization, as of the personnel in a business or government.

A series of events and processes that a company's management team facilitates in order to change and/or reorganize itself in an attempt to improve its current situation. Shakeups can occur when a business has undergone new ownership or has been performing poorly, and a shift in the company's team or overall strategy is a necessary catalyst for potential success.

Investopedia Says:
For example, Al Dunlap was brought to shake up Scott Paper in an attempt to make the paper company successful. Over the course of an 18-month process of restructuring and cost cutting, Dunlap transformed Scott Paper from a $2.9 billion company into $9.5 billion company.

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Rapid change in the management and structure of an organization. An organization undergoing a shakeup often experiences a period of trauma and uncertainty while the changes occur. The purpose of a shakeup is to change the direction and policies of an organization undergoing some form of stress.

noun

A thorough or drastic reorganization: overhaul. Informal housecleaning. See change/persist.