From Longman Business Dictionary
demergede·merge /ˌdiːˈmɜːdʒ-ˈmɜːrdʒ/ verb [intransitiveI, transitiveT]COMMERCE to make one part of a large company into a separate companyA plan was announced yesterday to demerge its North American operations.
—demerger noun [countableC]Merchant bankers proposed a demerger of the company into two separate businesses.