A corporate action in which an outside manager or management team purchases an ownership stake in the first company and replaces the existing management team. This type of action can occur due to a company appearing undervalued or having a poor management team.
Taobiz explains Management Buy-In - MBI
There are a wide range of management teams, such as hedge funds and other companies, that look for undervalued companies to purchase. If they find a company that fits with their investment criteria, they will often purchase the company and make it private to unlock the value. More often than not, they replace the management team with their own, which they feel will do a better job at running the company.