merger

n. result of the collaboration of two or more corporations into a single corporation, integration; fusion, agglomeration

The phrase mergers and acquisitions (abbreviated M&A) refers to the aspect of corporate strategy, corporate finance and management dealing with the buying, selling and combining of different companies  that can aid, finance, or help a growing company in a given industry grow rapidly without having to create another business entity.
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Noun
1. the combination of two or more commercial companies
(synonym) amalgamation, uniting
(hypernym) consolidation, integration
(derivation) unite, unify, merge
2. an occurrence that involves the production of a union
(synonym) fusion, unification
(hypernym) union
(derivation) unite, unify, merge

(n.)
One who, or that which, merges.
  

(n.)
An absorption of one estate, or one contract, in another, or of a minor offense in a greater.
  

(1) Acquisition in which all assets and liabilities are absorbed by the buyer. (2) More generally, any combination of two companies. The firm's activity in this respect is sometimes called M&A (Merger and Acquisition)