merger

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or an instance of merging.
• noun An absorption of one corporation by another, with the corporation being absorbed losing its separate identity and governance.
• noun Law An absorption of a lesser estate, contract, criminal offense, right, or liability into a succeeding larger one, resulting in the extinction of the former.

from The Century Dictionary.

• noun One who or that which merges.
• noun In the law of conveyancing, the sinking or obliteration of a lesser estate in lands, etc., resulting when it is transferred without qualification to the owner of a greater estate in the same property (or the like transfer of the greater estate to the owner of the lesser), if there be no intermediate estate.
• noun In the law of contracts, the extinguishment of a security for a debt by the creditor's acceptance of a higher security, such as a bond in lieu of a note, or a judgment in lieu of either: so called because such acceptance, by operation of law, and without intention of the parties, merges the lower security.
• noun A merging of the interests and control of two or more corporations, engaged in the same line, or in allied lines, of business, into a single corporation which exchanges its stock for that of the merging corporations, which however preserve, nominally at least, their separate identity.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who, or that which, merges.
• noun (Law) An absorption of one estate, or one contract, in another, or of a minor offense in a greater.
• noun The combining of two groups into a unified single group under a single leadership, with voluntary participation by the leaders or management of both groups.
• noun (Business, Finance) The combining of two commercial enterprises into a unified single enterprise under a single management, with voluntary participation by both parties. Compare acquisition and takeover.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act or process of merging two or more parts into a single unit.
• noun economics The legal union of two or more corporations into a single entity, typically assets and liabilities being assumed by the buying party.
• noun law An absorption of one or more estate(s) or contract(s) into one other, all being held by the same owner; of several counts of accusation into one judgement, etc.
• noun linguistics A type of sound change where two or more sounds merge into one.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the combination of two or more commercial companies
• noun an occurrence that involves the production of a union