The correct term is Demutualisation.
Before Demutualisation: Stock exchanges were often "mutual" organizations, where the members (brokers who trade on the exchange) were also the owners and managers.
After Demutualisation: The exchange is converted into a for-profit company.
The ownership (shares) and management are separated from the trading rights of the members.
The exchange is now owned by shareholders (who may or may not be brokers) and managed by a professional board, while members retain their rights to trade.
This process is done to improve governance, transparency, and efficiency.