From Longman Business Dictionary
amalgamatea·mal·ga·mate /əˈmælgəmeɪt/ verb [intransitiveI, transitiveT]COMMERCE if two organizations amalgamate or are amalgamated, they join together to form a bigger organizationThe two banks amalgamated earlier this year.
amalgamate withThe agency is expected to amalgamate with the National Rivers Authority.
It is a big job to amalgamate four companies.
—amalgamated adjectiveadjthe Amalgamated Clothing and Textile Workers Union