There are multiple definitions - click on the translation that matches your context.

fusión

full

merger

noun

Comparative law notes

Spain

if the reference is to a fusión por absorción

Definitions of merger

English

combination of usually two companies which results in effectively no transfer of control, and the two groups of shareholders are in a position to continue their shareholdings as before but on a combined basis

A merger of the two companies was the inevitable result after many years of co-operation.